#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int n, m = 0;
  cin >> n;
  while (n--) {
    int x, y;
    cin >> x >> y;
    m = max(m, x + y);
  }
  cout << m;
  return 0;
}
