#include <bits/stdc++.h>
int val(char c) {
  if (c >= 'A' && c <= 'Z') return c - 'A';
  return c - 'a';
}
int v[26];
int main(void) {
  int n;
  char s[1000];
  scanf("%d%s", &n, s);
  for (int i = 0; i < n; i++) {
    v[val(s[i])] = true;
  }
  bool ok = true;
  for (int i = 0; i < 26; i++) {
    if (!v[i]) ok = false;
  }
  printf("%s\n", ok ? "YES" : "NO");
}
