#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/rope>
using namespace std;
using namespace __gnu_pbds;
using namespace __gnu_cxx;
// /*
//                                                //////////**DEFINES - START**//////////
#define ret return
#define fi first
#define se second
#define mp make_pair
#define all(x) x.begin(), x.end()
#define be(x) x.begin()
#define en(x) x.end()
#define sz(x) ll(x.size())
#define for0(i, n) for (ll   i = 0; i < (n); ++i)
#define for1(i, n) for (ll   i = 1; i < (n); ++i)
#define rfor0(i, n) for (ll   i = (n) - 1; i >= 0; --i)
#define rfor1(i, n) for (ll   i = (n) - 1; i >= 1; --i)
#define rep(i, a, n) for (ll   i = a; i < ll(n); ++i)
#define rrep(i, a, n) for (ll   i = a - 1; i >= ll(n); --i)
#define popcount __builtin_popcountll
#define fastIO() ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define con continue
#define pb push_back
#define pob pop_back
#define deb(x) cout << (#x) << " is " << (x) << endl
#define ins insert
#define len(s) (s).length()
#define gi greater<int>()
#define gll greater<ll  >()
#define gstr greater<string>()
#define gpll greater<pair<ll  , ll  >>()
#define rast(x1, y1, x2, y2) sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2))
#define rev reverse
#define ub upper_bound
#define lb lower_bound
#define bs binary_search
#define rs resize
#define last(a) a.back()
#define co count
#define ba(a) a.back()
#define um unordered_map
#define rsun(a) a.resize(unique(a.begin(), a.end())-a.begin())
#define endl '\n'
#ifdef OG_Matveychick1
bool local = true;
#else
bool local = false;
#endif
//                                                \\\\\\\\\\**DEFINES - END**\\\\\\\\\\
        // */
// /*
//                                                //////////**TYPEDEFS - START**//////////
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<char> vc;
typedef pair<int, int> pii;
typedef vector<pii> vpii;
typedef vector<string> vs;
typedef long long ll;
typedef unsigned long long ull;
typedef vector<ull> vull;
typedef pair<ll, ll> pll;
typedef vector<ll> vll;
typedef vector<pll> vpll;
typedef pair<double, double> pdd;
typedef long double ld;
typedef double D;
typedef vector<ld> vld;
typedef vector<pair<ld, ld> >
        vpld;
typedef string str;
typedef set<ll> sll;
typedef set<int> si;
typedef set<str> ss;
typedef set<pii> spii;
typedef multiset<int> msi;
typedef multiset<ll> msll;
typedef multiset<str> mss;
typedef multiset<pii> mspii;
typedef multiset<pll> mspll;
typedef map<str, str> mps;
typedef map<int, int> mpi;
typedef map<ll, ll> mpll;
typedef map<int, vi> mpvi;
typedef map<int, vll> mpvll;
typedef map<char, int> mpci;
typedef multimap<ll, ll> mmpll;
typedef multimap<str, str> mmps;
typedef multimap<int, int> mmpi;
typedef vector<vector<int> > vvi;
typedef vector<vector<ll> > vvll;
typedef vector<vector<long double> > vvld;
typedef vector<vvi> vvvi;
typedef vector<vector<char> > vvc;
typedef vector<vs> vvs;
typedef vector<D> vD;
typedef set<pair<ll, ll> >
        spll;
typedef pair<ull, ull> pull;
typedef vector<pull> vpull;
typedef vector<bool> vb;
typedef vector<vb> vvb;
typedef set<char> sc;
typedef queue<int> qi;
typedef queue<ll> qll;
typedef queue<bool> qb;
typedef vector<sll> vsll;
typedef queue<pair<ll, ll> >
        qpll;
typedef vector<vector<pair<int, int> > >
        vvpii;
typedef vector<vector<pair<ll, ll> > >
        vvpll;
typedef vector<spll> vspll;
typedef multiset<char> msc;
typedef queue<str> qs;
typedef vector<set<int> > vsi;
typedef priority_queue<ll> pqll;
typedef vector<vsll> vvsll;
typedef pair<ld, ld> pld;
typedef vector<vvll> vvvll;
typedef set<ld> sld;
typedef vector<vpld> vvpld;
typedef tree<ll, null_type, less<ll>, rb_tree_tag, tree_order_statistics_node_update>
        ordered_set;
typedef tree<ll, null_type, less_equal<ll>, rb_tree_tag, tree_order_statistics_node_update>
        ordered_multiset;
//                                                \\\\\\\\\\**TYPEDEFS - END**\\\\\\\\\\
        // */
// /*
//                                                //////////**CONSTANTS - START**//////////
const ld pi = acosl(-1);
const ll mod1 = 1e9 + 7;
const ll mod2 = 998244353;
const ll MAXLL = 9223372036854775807;
//const ll MAXINT = 2147483647;
const ld eps = 1e-9;
//                                                \\\\\\\\\\**CONSTANTS - END**\\\\\\\\\\
        // */
// /*
//                                                //////////**TEMPLATES - START**//////////
template<typename T>
istream &operator>>(istream &in, vector<T> &a) {
    for (T &i : a) in >> i;
    return in;
}
template<typename T1, typename T2>
istream &operator>>(istream &in, pair<T1, T2> &a) {
    in >> a.fi >> a.se;
    return in;
}
template<typename T1, typename T2>
ostream &operator<<(ostream &out, pair<T1, T2> a) {
    out << a.fi << " " << a.se;
    return out;
}
template<typename T1, typename T2>
istream &operator>>(istream &in, vector<pair<T1, T2> >
&a) {
    for (
        pair<T1, T2> &i
            : a)
        in >> i.fi >> i.
                se;
    return
            in;
}
template<typename T>
ostream &operator<<(ostream &out, const vector<T> &a) {
    for (auto i : a) {
        out << i << " ";
    }
    return out;
}
template<typename T1, typename T2>
ostream &operator<<(ostream &out, vector<pair<T1, T2> >
&a) {
    for (
        pair<T1, T2> i
            : a)
        out << i.fi << " " << i.se <<
            endl;
    return
            out;
}
template<typename T1>
ostream &operator<<(ostream &out, vector<vector<T1> > &a) {
    for (vector<T1> i : a) {
        for (T1 j : i) out << j << " ";
        out << endl;
    }
    return out;
}
template<typename T1, typename T2>
inline T1 min(T1 a, T2 b) {
    b = (T1) b;
    return a > b ? b : a;
}
template<typename T1, typename T2>
inline T1 max(T1 a, T2 b) {
    b = (T1) b;
    return a > b ? a : b;
}
template<typename T1, typename T2>
inline void amin(T1 &a, T2 b) {
    a = min(a, b);
}
template<typename T1, typename T2>
inline void amax(T1 &a, T2 b) {
    a = max(a, b);
}
//                                                \\\\\\\\\\**TEMPLATES - END**\\\\\\\\\\
        // */
// This bear is a good alternative to duck!!!
/*
    ????      ??????
  ???????????????????
 ????????????????  ???
???   ???????????  ???
???  ???????????? ??
 ??????????????????
   ??????????????? ?
   ?????????????????
   ???????   ???    ??
    ????  ??????????
     ????     ?? ???
   ???????????? ?????
  ????????????????????
 ????????   ??  ???????
 ???????         ?????
 */
ld getTime() {
    return (ld) clock() / (ld) CLOCKS_PER_SEC;
}
mt19937_64 rn(chrono::steady_clock::now().time_since_epoch().count());
//mt19937_64 rn(35);
ll rnd(ll l, ll r) {
    ll a = rn() % (r - l + 1) + l;
    return a;
}
void solve();
ll T = 1;
signed main(int argc, char **argv) {
    //    setlocale(LC_ALL, "RUS");
    fastIO()
    cout.precision(12);
    cout << fixed;
    if (local && argc == 1) {
        freopen("input.txt", "r", stdin);
//        freopen("wrong.txt", "w", stdout);
    }
//    cin >> T;
    while (T--) {
        solve();
    }
    if (local && argc == 1) {
        cout << endl << fixed << "time = " << getTime();
    }
    return 0;
}
/*
    ___        __              __   ______          __        _____ __             __          __  __
   /   | _____/ /___  ______ _/ /  / ____/___  ____/ /__     / ___// /_____ ______/ /______   / / / /__  ________
  / /| |/ ___/ __/ / / / __ `/ /  / /   / __ \/ __  / _ \    \__ \/ __/ __ `/ ___/ __/ ___/  / /_/ / _ \/ ___/ _ \
 / ___ / /__/ /_/ /_/ / /_/ / /  / /___/ /_/ / /_/ /  __/   ___/ / /_/ /_/ / /  / /_(__  )  / __  /  __/ /  /  __/
/_/  |_\___/\__/\__,_/\__,_/_/   \____/\____/\__,_/\___/   /____/\__/\__,_/_/   \__/____/  /_/ /_/\___/_/   \___/
*/
const ll N = 85, inf = 1e15;
ll n, k, h[N], c[N], dp1[N][N][N], dp2[N][N][N], cm[N], mc[N], alc[N], pc[N], ans = inf;
void solve() {
    cin >> n >> k;
    for0(i, N) mc[i] = inf;
    for0(cnt, N) for0(mn, N) for0(so, N) dp1[cnt][mn][so] = dp2[cnt][mn][so] = inf;
    dp1[0][n][1] = 0;
    for0(i, n) cin >> h[i] >> c[i], h[i]++, cm[h[i]]++, alc[i] = c[i];
    sort(alc, alc + n), alc[n] = inf;
    for0(i, n) pc[i] = lb(alc, alc + n + 1, c[i]) - alc;
    for0(i, n) amin(mc[h[i]], pc[i]);
    partial_sum(cm, cm + N, cm);
    for1(i, N) amin(mc[i], mc[i - 1]);
    for1(i, N) {
        for0(cnt0, cm[i - 1] + 1) {
            rep(cnt1, cnt0 + (cm[i] != cm[i - 1]), cm[i] + 1) {
                if (cnt1 != cnt0 && cnt1 != cm[i] && cnt1 != cnt0 + 1) con;
                for0(mn, n + 1) {
                    for0(so, cnt0 + 2) {
                        ll nso = so, pl = 0;
                        if (so >= cnt1 - cnt0) nso -= cnt1 - cnt0;
                        else nso = 0, pl += alc[mn] * (cnt1 - cnt0 - so);
                        nso += cnt1 - cnt0;
                        amin(dp2[cnt1][(cnt0 == cnt1 ? mn : min(mn, mc[i]))][nso],
                             dp1[cnt0][mn][so] + pl + i * (cnt1 - cnt0) * k);
                    }
                }
            }
        }
        swap(dp1, dp2);
        for0(cnt, N) for0(mn, N) for0(so, N) dp2[cnt][mn][so] = inf;
    }
    for0(mn, N) for0(so, N) amin(ans, dp1[n][mn][so]);
    cout << ans - k * accumulate(h, h + n, 0ll);
}
Compilation message (stderr)
Main.cpp: In function 'int main(int, char**)':
Main.cpp:291:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  291 |         freopen("input.txt", "r", stdin);
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