#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n, current = -1;
  cin >> n;
  for (int i = 1; i <= n; i++) {
    long long x, y;
    cin >> x >> y;
    current = max(x + y, current);
  }
  cout << current;
  return 0;
}
