PROG-1117: ภารกิจ (mission)

#include <bits/stdc++.h>

using namespace std;
using lli = long long;
lli ar[100010];
int n;

int main(){

    scanf("%d", &n);

    for(int i=1;i<=n;i++){
        lli A, B;
        scanf("%lld%lld", &A, &B);
        ar[i] = B - 2*A;
    }

    sort(ar+1, ar+n+1);

    lli mx = 0, sum = 0;
    for(int i=1;i<=n;i++){
        if(sum + ar[i] > sum - (2*i - 1))
            sum += ar[i];
        else
            sum -= 2*i - 1;
    }

    printf("%lld", sum);

    return 0;
}

/*
1 = 1
2 = 4 = 1 + 3
3 = 9 = 1 + 3 + 5
4 = 16 = 1 + 3 + 5 + 7
*/