#include<bits/stdc++.h>
using namespace std;
#define all(x) (x).begin(), (x).end()
#define sz(x) ( (int)(x).size() )
using LL = long long;
template<class T>
inline bool asMn(T &a, const T &b) { return a > b ? a = b, true : false; }
template<class T>
inline bool asMx(T &a, const T &b) { return a < b ? a = b, true : false; }
const LL infLL = 1e18;
mt19937 rng( (uint32_t)chrono::steady_clock::now().time_since_epoch().count() );
template<class T>
struct Bit {
vector<T> a;
Bit(int nNode = 0) { a.assign(nNode, T() ); }
void reset(int nNode = 0) { a.assign(nNode, T() ); }
void upd(int pos, int val) {
for (int i = pos; i < sz(a); i |= i + 1) a[i] += val;
}
T get(int pos) {
T ret = 0;
for (int i = pos; i >= 0; i = (i & (i + 1) ) - 1) ret += a[i];
return ret;
}
int findPos(int val) {
int ret = 0;
for (int i = __lg(sz(a) ); i >= 0; --i) {
ret ^= 1 << i;
if (ret < sz(a) && a[ret - 1] <= val) val -= a[ret - 1];
else ret ^= 1 << i;
}
return ret;
}
};
Bit<int> cnt;
Bit<LL> sum;
int n, m;
vector<pair<int, int> > piece;
vector<int> lable;
int l = 1, r = 0;
LL get(int Left, int Right) {
while (r < Right) cnt.upd(lable[++r], 1), sum.upd(lable[r], piece[r].second);
while (l > Left) cnt.upd(lable[--l], 1), sum.upd(lable[l], piece[l].second);
while (r > Right) cnt.upd(lable[r], -1), sum.upd(lable[r], -piece[r].second), --r;
while (l < Left) cnt.upd(lable[l], -1), sum.upd(lable[l], -piece[l].second), ++l;
return sum.get(cnt.findPos(m - 1) );
}
LL ans = -infLL;
void solve(int Left, int Right, int bestL, int bestR) {
int Mid = (Left + Right) >> 1;
LL ret = -infLL;
int bestM = bestL;
for (int i = bestL; i <= min(bestR, Mid - m - 1); ++i) {
LL tmp = get(i + 1, Mid - 1) + piece[i].second + piece[Mid].second - ( (piece[Mid].first - piece[i].first) << 1);
if (tmp > ret) {
ret = tmp;
bestM = i;
}
}
asMx(ans, ret);
if (Left < Mid) solve(Left, Mid - 1, bestL, bestM);
if (Mid < Right) solve(Mid + 1, Right, bestM, bestR);
}
int main() {
ios_base::sync_with_stdio(0); cin.tie(0);
#ifdef FourLeafClover
freopen("input", "r", stdin);
#endif // FourLeafCLover
cin >> n >> m; m -= 2;
piece.assign(n, {} );
for (int i = 0; i < n; ++i) cin >> piece[i].second >> piece[i].first;
sort(all(piece) );
vector<pair<int, int> > com;
for (int i = 0; i < n; ++i) com.emplace_back(piece[i].second, i);
sort(all(com) );
lable.assign(n, 0);
for (int i = 0; i < n; ++i) lable[i] = n - 1 - (int)(lower_bound(all(com), make_pair(piece[i].second, i) ) - com.begin() );
cnt.reset(n);
sum.reset(n);
solve(0, n - 1, 0, n - 1);
cout << ans << '\n';
return 0;
}
