#include <bits/stdc++.h>
using namespace std;
int i, j, k;
int fr[] = {0, 0, 1, -1, -1, 1, -1, 1};
int fc[] = {-1, 1, 0, 0, 1, 1, -1, -1};
int main() {
  ios_base::sync_with_stdio(false);
  long long n, x, y, xf, yf, mx = 0;
  long long d = 0;
  cin >> n;
  for (i = 1; i <= n; i++) {
    cin >> x >> y;
    d = max(x + y, d);
  }
  cout << d << endl;
  return 0;
}
