#include <bits/stdc++.h>   using namespace std;   int main() {     int n, c, d, a, b, i;     cin >> n >> a >> b;     c = b, d = c;     for (i = 2; i <= n; i++) {       cin >> a >> b;       c = max(c, d - a + b);       d = d - a + b;     }     cout << c;     return 0;   }   