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