#include <bits/stdc++.h>
using namespace std;
const int M = 1e9 + 7;
long long powmod(long long a, long long b, long long mod) {
  long long res = 1;
  a %= mod;
  assert(b >= 0);
  for (; b; b >>= 1) {
    if (b & 1) res = res * a % mod;
    a = a * a % mod;
  }
  return res % mod;
}
const int N = 1e5 + 10;
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int n;
  cin >> n;
  vector<pair<int, int> > pt(n);
  for (int i = 0; i < n; ++i) cin >> pt[i].first >> pt[i].second;
  sort(pt.begin(), pt.end());
  int ans = 0;
  for (int i = 0; i < n; ++i) ans = max(ans, pt[i].first + pt[i].second);
  cout << ans << endl;
  return 0;
}
