#define local
#ifndef local
#include ""
#endif
#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
using namespace std;
#define int long long
#define fi first
#define se second
#define pb push_back
#define mp make_pair
typedef pair<int, int> ii;
typedef pair<ii, int> iii;
typedef pair<ii, ii> iiii;
const int N = 3e5 + 5;
const int oo = 1e18 + 7, mod = 1e9 + 7;
mt19937 rng(1);
int rnd(int l, int r){
int temp = rng() % (r - l + 1);
return abs(temp) + l;
}
int n, m;
ii arr[N];
int v[N], c[N];
int answer = -oo;
vector<int> diff;
int pos[N];
bool cmp(ii a, ii b){
return a.se < b.se;
}
int lstl, lstr;
int sum[N << 2], num[N << 2];
int IT[N << 2];
void upd(int id, int l, int r, int pos, int val){
if(l == r){
sum[id] += diff[l] * val;
num[id] += val;
return;
}
int mid = (l + r) >> 1;
if(pos <= mid) upd(id << 1, l, mid, pos, val);
else upd(id << 1 | 1, mid + 1, r, pos, val);
sum[id] = sum[id << 1] + sum[id << 1 | 1];
num[id] = num[id << 1] + num[id << 1 | 1];
}
int tol(int id, int l, int r, int rem){
if(l == r){
if(rem > num[id]) return -oo;
return rem * diff[l];
}
int mid = (l + r) >> 1;
if(num[id << 1] >= rem) return tol(id << 1, l, mid, rem);
else return sum[id << 1] + tol(id << 1 | 1, mid + 1, r, rem - num[id << 1]);
}
void mov(int le, int ri){
while(lstl > le){
lstl--;
upd(1, 1, diff.size() - 1, pos[lstl], 1);
}
while(lstr < ri){
lstr++;
upd(1, 1, diff.size() - 1, pos[lstr], 1);
}
while(lstl < le){
upd(1, 1, diff.size() - 1, pos[lstl], -1);
lstl++;
}
while(lstr > ri){
upd(1, 1, diff.size() - 1, pos[lstr], -1);
lstr--;
}
}
int get(){
return tol(1, 1, diff.size() - 1, m - 2);
}
void dncdp(int l, int r, int optl, int optr){
if(l > r) return;
int temp1 = lstl, temp2 = lstr;
if(optl == optr){
for(int i = l; i <= r; i++){
mov(optl + 1, i - 1);
// cout << optl << " " << i << "\n";
answer = max(answer, get() + v[optl] + 2 * c[optl] + v[i] - 2 * c[i]);
}
return;
}
int mid = (l + r) >> 1;
ii maxi = {-oo, -oo};
for(int i = optl; (i <= optr) && ((i + 2) <= mid); i++){
mov(i + 1, mid - 1);
maxi = max(maxi, {get() + v[i] + 2 * c[i] + v[mid] - 2 * c[mid], i});
}
//cout << maxi.se << " " << mid << "\n";
answer = max(answer, maxi.fi);
dncdp(l, mid - 1, optl, maxi.se);
dncdp(mid + 1, r, maxi.se, optr);
mov(temp1, temp2);
}
#ifdef local
void process(){
cin >> n >> m;
for(int i = 1; i <= n; i++) cin >> arr[i].fi >> arr[i].se;
sort(arr + 1, arr + n + 1, cmp);
for(int i = 1; i <= n; i++){
v[i] = arr[i].fi;
c[i] = arr[i].se;
}
diff.pb(oo);
for(int i = 1; i <= n; i++) diff.pb(arr[i].fi);
sort(diff.begin(), diff.end());
diff.resize(unique(diff.begin(), diff.end()) - diff.begin());
reverse(diff.begin(), diff.end());
for(int i = 1; i <= n; i++){
int le = 1, ri = diff.size() - 1;
while(le < ri){
int mid = (le + ri) >> 1;
if(diff[mid] > v[i]) le = mid + 1;
else ri = mid;
}
pos[i] = le;
}
lstl = 1, lstr = 0;
dncdp(m, n, 1, n - m + 1);
cout << answer;
}
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
process();
}
#endif
