#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, i, j, m, k, ma = 0;
  cin >> n;
  for (i = 0; i < n; i++) {
    cin >> m >> k;
    int c = m + k;
    if (c > ma) ma = c;
  }
  cout << ma << endl;
  return 0;
}
