//#pragma GCC optimize("Ofast,unroll-loops,O3")
//#pragma GCC optimize("avx,avx2,sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,fma,tune=native")
#include<bits/stdc++.h>
//#include<bits/extc++.h>
//#pragma pack(1)
#define fast ios::sync_with_stdio(0); cin.tie(0);
#define int long long
#define pii pair<int,int>
#define x first
#define y second
#define N 200015
using namespace std;
//using namespace __gnu_pbds;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
//typedef tree<int, null_type,less_equal<int>, rb_tree_tag,tree_order_statistics_node_update> order_multiset;
//typedef tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update> order_set;
int n,m;
pii arr[N];
bool cmp(pii a,pii b){
int dy=a.y-b.y;
int dx=a.x-b.x;
return dy*2<dx;
}
signed main(){
fast
cin>>n>>m;
for (int i=1;i<=n;i++)
cin>>arr[i].x>>arr[i].y;
sort(arr+1,arr+1+n,cmp);
int mx=0,mn=1e18,total=0;
for (int i=1;i<=m;i++){
mx=max(mx,arr[i].y);
mn=min(mn,arr[i].y);
total+=arr[i].x;
}
cout<<total-(mx-mn)*2<<'\n';
}
