#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int n, a, b, r, r1 = 0;
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> a >> b;
    r = a + b;
    if (r1 < r) {
      r1 = r;
    }
  }
  cout << r1;
}
