#include <bits/stdc++.h>
using namespace std;
int main() {
  vector<int> result;
  int n, x, y;
  cin >> n;
  while (n--) {
    cin >> x >> y;
    int store = x + y;
    result.push_back(store);
  }
  sort(result.begin(), result.end());
  int maxxpoint = result.back();
  cout << maxxpoint;
  return 0;
}
