#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, x, y;
  scanf("%d", &n);
  long long mins = 0;
  for (int i = 0; i < n; i++) {
    scanf("%d%d", &x, &y);
    mins = max(mins, (long long)(y + x));
  }
  cout << mins << endl;
}
