#include <bits/stdc++.h>
using namespace std;
const double pi = acos(-1);
const long long INF = 1LL << 50;
int n, res;
int main() {
  int i, l, r;
  while (cin >> n) {
    cin >> l >> r;
    res = l + r;
    for (i = 1; i < n; i++) {
      cin >> l >> r;
      res = max(res, l + r);
    }
    cout << res << '\n';
  }
  return 0;
}
