#include <bits/stdc++.h>
using namespace std;
long long int n, maxi = 0;
int main() {
  cin >> n;
  long long int a[n][2];
  for (long long int i = 0; i < n; i++) {
    cin >> a[i][0] >> a[i][1];
    a[i][0] += a[i][1];
    if (maxi <= a[i][0]) maxi = a[i][0];
  }
  cout << maxi;
  return 0;
}
