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