#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  long long x, y, n, ans = -1;
  cin >> n;
  while (n--) {
    cin >> x >> y;
    ans = max(ans, x + y);
  }
  cout << ans;
  return 0;
}
