#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pll pair<long long, long long>
#define pb push_back
#define F first
#define S second
#define all(x) (x).begin(), (x).end()
const ll N = 3e5 + 100;
const ll inf = 1e18;
const ll mod = 1e9 + 7;
const ll blocks = 350;
ll n,m;
pll a[N];
ll dp[2024][2024];
void to_thic_cau(){
cin >> n >> m;
for(int i = 1; i <= n;i++) cin >> a[i].F >> a[i].S;
sort(a + 1, a + n + 1, [&](const pll &a, const pll &b){
return a.S < b.S;
});
for(int i = 0; i <= n;i++){
for(int j = 0; j <= m;j++) dp[i][j] = -inf;
}
for(int i = 1; i <= n;i++){
for(int j = 1; j <= m;j++){
if(j == 1) dp[i][j] = max(dp[i-1][j], a[i].F + 2 * a[i].S);
else if(j == m) dp[i][j] = max(dp[i-1][j], dp[i-1][j-1] + a[i].F - 2 * a[i].S);
else dp[i][j] = max(dp[i-1][j], dp[i-1][j-1] + a[i].F);
}
}
cout << dp[n][m] << '\n';
}
signed main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
ll tc = 1;
//cin >> tc;
while(tc--) to_thic_cau();
}
