#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, i, x, y, z, temp, ans;
  while (cin >> n) {
    cin >> x >> y;
    temp = x + y;
    if (n == 1) {
      cout << temp << endl;
      continue;
    }
    for (i = 1; i < n; i++) {
      cin >> x >> y;
      z = x + y;
      ans = max(temp, z);
      temp = ans;
    }
    cout << ans << endl;
  }
  return 0;
}
