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