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