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