#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  long long x[n], y[n], i;
  long long maxi = LLONG_MIN;
  for (i = 0; i <= n - 1; i++) {
    cin >> x[i] >> y[i];
    maxi = max(maxi, x[i] + y[i]);
  }
  cout << maxi;
}
