#include <bits/stdc++.h>
using namespace std;
using vi = vector<int>;
using vvi = vector<vi>;
using vs = vector<string>;
using vb = vector<bool>;
using ll = long long;
int main() {
  int n;
  cin >> n;
  int k = 0;
  for (int i = 0; i < n; ++i) {
    int x, y;
    cin >> x >> y;
    k = max(k, x + y);
  }
  cout << k << endl;
}
