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