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