#include <bits/stdc++.h>
int main() {
  int n;
  scanf("%d", &n);
  char word[n + 1];
  scanf("%s", word);
  char lower_word[n + 1];
  int parts[26];
  for (int u = 0; u < 26; u++) {
    parts[u] = 0;
  }
  for (int i = 0; i < n; i++) {
    lower_word[i] = toupper(word[i]);
  }
  for (int j = 65; j < 91; j++) {
    for (int k = 0; k < n; k++) {
      if (j == (int)lower_word[k]) {
        parts[j - 65] += 1;
      }
    }
  }
  int nzeroes = 0;
  for (int i = 0; i < 26; i++) {
    if (parts[i] == 0) {
      nzeroes += 1;
      break;
    }
  }
  if (nzeroes > 0) {
    printf("NO");
  } else {
    printf("YES");
  }
  return 0;
}
