#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("Ofast")
void solve() {
  int t;
  cin >> t;
  int a[26]{};
  for (; t--;) {
    char b;
    cin >> b;
    b = tolower(b);
    a[b - 'a'] = 1;
  }
  for (auto i : a) {
    if (i == 0) {
      cout << "NO" << endl;
      return;
    }
  }
  cout << "YES" << endl;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  solve();
  return 0;
}
