#include <iostream>
#include <map>
#include <vector>
#include <climits>
#include <stack>
#include <string>
#include <queue>
#include <algorithm>
#include <set>
#include <unordered_set>
#include <iostream>
#include <unordered_map>
#include <cmath>
#include <cctype>
#include <bitset>
#include <iomanip>
#include <cstring>
using namespace std;
#define int long long
#define pii pair<int, int>
#define mp make_pair
int n, m, ans=LLONG_MIN, R=1, L=1;
vector<pii> vect, temp;
vector <int> ft, disc, ft2;
int query(int index){
int sum = 0;
while (index>0){
sum+=ft[index];
index-= index & (-index);
}
return sum;
}
void update(int index, int val){
while (index<=n){
ft[index]+=val;
index+=index&(-index);
}
}
int query2(int index){
int sum = 0;
while (index>0){
sum+=ft2[index];
index-= index & (-index);
}
return sum;
}
void update2(int index, int val){
while (index<=n){
ft2[index]+=val;
index+=index&(-index);
}
}
int f(int l, int r){
if (r-l+1<m)return LLONG_MIN/2;
while (L>l)--L, update(disc[L], vect[L].second), update2(disc[L], 1);
while (R<r)++R, update(disc[R], vect[R].second), update2(disc[R], 1);
while (L<l)update(disc[L], -vect[L].second), update2(disc[L], -1), ++L;
while (R>r)update(disc[R], -vect[R].second), update2(disc[R], -1), --R;
int low=0, high=n+1;
while (low+1<high){
int mid=(low+high)/2;
if (query2(mid)<=m)low=mid;
else high=mid;
}
return query(low);
}
void dnc(int l, int r, int optl, int optr){
if (l>r)return;
int best=LLONG_MIN/2, opt=1, mid=(l+r)/2;
for (int i=min(mid, optr); i>=optl; --i){
int res=f(i, mid)-2*(vect[mid].first-vect[i].first);
if (res>best)best=res, opt=i;
}
ans=max(ans, best);
dnc(l, mid-1, optl, opt);
dnc(mid+1, r, opt, optr);
}
int32_t main(){
cin>>n>>m;
vect.resize(n+1, mp(LLONG_MIN/2, LLONG_MIN/2));
disc.resize(n+1);
ft.resize(n+1, 0);
ft2.resize(n+1, 0);
temp.resize(n);
for (int i=1; i<=n; ++i)cin>>vect[i].second>>vect[i].first;
sort(vect.begin(), vect.end());
for (int i=1; i<=n; ++i)temp[i-1]=mp(vect[i].second, i);
sort(temp.begin(), temp.end(), greater<pii>());
for (int i=0; i<n; ++i)disc[temp[i].second]=i+1;
L=R=temp[0].second;
update(1, temp[0].first);
update2(1, 1);
dnc(1, n, 1, n);
cout<<ans;
}
