#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  long long x, y, mx = INT_MIN;
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> x >> y;
    mx = max(mx, x + y);
  }
  cout << mx << endl;
  return 0;
}
