#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  cin >> n;
  int M = 0;
  for (int i = 0; i < n; i++) {
    int x, y;
    cin >> x >> y;
    if (x + y > M) M = x + y;
  }
  cout << M << endl;
}
