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