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