#include <bits/stdc++.h>
using namespace std;
vector<long long int> v[2002];
const long long int N = 7e5 + 6;
const long long int M = 1e9 + 7;
map<long long int, long long int> a, h;
int main() {
  long long int n;
  cin >> n;
  long long int maxm = 0;
  while (n--) {
    long long int a, b;
    cin >> a >> b;
    if (maxm < a + b) maxm = a + b;
  }
  cout << maxm;
}
