#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  bool alpha[28];
  memset(alpha, 0, sizeof alpha);
  char temp;
  int cnt = 0;
  while (n--) {
    cin >> temp;
    if (!alpha[tolower(temp) - 'a']) {
      ++cnt;
      alpha[tolower(temp) - 'a'] = true;
    }
  }
  printf(((cnt == 26) ? "YES" : "NO"));
}
