#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int ex, enter, remain = 0, ans = 0;
  for (int i = 0; i < n; i++) {
    cin >> ex >> enter;
    remain = remain - ex + enter;
    ans = max(ans, remain);
  }
  cout << ans;
  return 0;
}
