#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int a[n + 1], b[n + 1];
  for (int i = 1; i <= n; i++) {
    cin >> a[i] >> b[i];
  }
  int mx = -1;
  int now = 0;
  for (int i = 1; i <= n; i++) {
    now -= a[i];
    now += b[i];
    mx = max(now, mx);
  }
  cout << mx;
}
