//Sylwia Sapkowska
#include <bits/stdc++.h>
#pragma GCC optimize("O3", "unroll-loops")
using namespace std;
void __print(int x) {cerr << x;}
void __print(long long x) {cerr << x;}
void __print(long double x) {cerr << x;}
void __print(char x) {cerr << '\'' << x << '\'';}
void __print(const char *x) {cerr << '\"' << x << '\"';}
void __print(const string &x) {cerr << '\"' << x << '\"';}
void __print(bool x) {cerr << (x ? "true" : "false");}
template<typename T, typename V>
void __print(const pair<T, V> &x) {cerr << '{'; __print(x.first); cerr << ", "; __print(x.second); cerr << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cerr << '{'; for (auto &i: x) cerr << (f++ ? ", " : ""), __print(i); cerr << "}";}
void _print() {cerr << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cerr << ", "; _print(v...);}
#ifdef LOCAL
#define debug(x...) cerr << "[" << #x << "] = ["; _print(x)
#else
#define debug(x...)
#endif
#define int long long
typedef pair<int, int> T;
const int oo = 1e18, oo2 = 1e9+7, K = 30;
const int mod = 998244353;
void solve(){
int n, m; cin >> n >> m;
vector<T>a;
for (int i = 0; i<n; i++){
int s, c; cin >> s >> c;
a.emplace_back(c, s);
}
sort(a.begin(), a.end());
int L = 0, R = n-1;
multiset<int>A, B;
int ret = 0;
int sum = 0;
auto add = [&](int v){
if ((int)A.size() < m-2){
A.insert(v);
sum += v;
return;
}
if (*A.begin() < v){
A.insert(v);
sum += v;
sum -= *A.begin();
B.insert(*A.begin());
A.erase(A.begin());
} else {
B.insert(v);
}
};
auto remove = [&](int v){
auto it = A.find(v);
if (it != A.end()) {
A.erase(it);
sum -= v;
if ((int)A.size() < m-2){
if (B.size()){
A.insert(*B.rbegin());
sum += *B.rbegin();
B.erase((--(B.end())));
}
}
} else {
B.erase(B.find(v));
}
};
auto fit = [&](int l, int r){
while (L > l){
L--;
add(a[L].second);
}
while (R < r){
R++;
add(a[R].second);
}
while (L < l){
remove(a[L].second);
L++;
}
while (R > r){
remove(a[R].second);
R--;
}
};
for (int i = 0; i<n; i++) add(a[i].second);
function<void(int, int, int, int)>rec = [&](int l, int r, int la, int lb){
if (l > r) return;
int mid = (l+r)/2;
int opt = n-1;
int ans = -oo;
for (int i = la; i<min(mid, lb); i++){
fit(i+1, mid-1);
if (A.size() == m-2){
int maybe = 2*a[i].first + a[i].second + sum + a[mid].second - 2 * a[mid].first;
if (ans < maybe){
opt = i;
ans = maybe;
}
}
// i, mid??
}
ret = max(ret, ans);
rec(l, mid-1, la, opt);
rec(mid+1, r, opt, lb);
};
rec(0, n-1, 0, n-1);
cout << ret << "\n";
}
int32_t main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int t = 1;
// cin >> t;
while (t--) solve();
return 0;
}
