#include <bits/stdc++.h>
#include "ext/pb_ds/assoc_container.hpp"
#include "ext/pb_ds/tree_policy.hpp"
using namespace std;
using namespace __gnu_pbds;
#define f first
#define s second
typedef long long ll;
typedef tree<pair<ll, ll>, null_type, less<pair<ll, ll>>,
rb_tree_tag, tree_order_statistics_node_update> oset;
const int N = 2e5+5;
ll n, k, cur, ans, l, cnt;
pair<ll, ll> p[N];
oset s, tmp;
int main()
{
cin >> n >> k;
for(int i=0; i<n; i++) cin >> p[i].s >> p[i].f;
sort(p, p+n);
for(int i=0; i<k; i++)
{
if(i >= 1 && i < k-1) s.insert({p[i].s, i}), tmp.insert({i, p[i].s});
cur += p[i].s;
}
cur += p[0].f*2 - p[k-1].f*2;
ans = max(cur, ans);
for(int i=k; i<n; i++)
{
ll a = cur - p[i-1].s + p[i-1].f*2 + p[i].s - p[i].f*2;
auto x = *tmp.find_by_order(0);
ll idx = x.f;
ll b = cur + p[i-1].f*2 + p[i].s - p[i].f*2 - p[l].s - p[l].f*2 + p[idx].f*2;
x = *s.find_by_order(0);
ll c = cur + p[i-1].f*2 + p[i].s - p[i].f*2 - x.f;
if(a >= b && a >= c) cur = a;
if(b >= c && b >= a)
{
x = *tmp.find_by_order(0);
l = x.f;
tmp.erase(x);
s.erase({x.s, x.f});
s.insert({p[i-1].s, i-1}), tmp.insert({i-1, p[i-1].s});
cur = b;
}
if(c >= a && c >= b)
{
x = *s.find_by_order(0);
s.erase(x), tmp.erase({x.s, x.f});
s.insert({p[i-1].s, i-1}), tmp.insert({i-1, p[i-1].s});
cur = c;
}
x = *tmp.find_by_order(0);
idx = x.f;
cnt = max(cnt, l+1);
while(cnt < idx)
{
if(p[l].s + p[l].f*2 <= p[cnt].s + p[cnt].f*2) l = cnt;
cnt++;
}
ans = max(ans, cur);
}
cout << ans << endl;
}
