#include <bits/stdc++.h>
using namespace std;
long long sum, tot, mx = -1e18, mn = 1e18, a, b, c, d, k, t, s, m, n, x, y, z;
bool ok = 0;
set<long long> se;
deque<long long> q;
vector<long long> v;
map<long long, long long> mp;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cin >> t;
  while (t--) {
    cin >> x >> y;
    mx = max(x + y, mx);
  }
  cout << mx;
  return 0;
}
