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