#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1e5;
const int SN = 105;
void solve() {
  int n;
  cin >> n;
  int mx = 0;
  for (int i = 0; i < n; i++) {
    int x, y;
    cin >> x >> y;
    mx = max(mx, x + y);
  }
  cout << mx << '\n';
}
int main() {
  int t;
  t = 1;
  while (t--) {
    solve();
  }
}
