#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("-O2")
const int LIM = 5e5 + 5, MOD = 1e9 + 7;
int t, n, m, k, x, y;
bool compare(pair<int, int> p1, pair<int, int> p2) {
  return p1.second < p2.second;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  ;
  cin >> n;
  long long ans = 0;
  for (int i = 0; i < n; i++) {
    cin >> x >> y;
    if (x + y > ans) ans = x + y;
  }
  cout << ans;
}
