#include <bits/stdc++.h>
int main() {
  int n, i, j, beta1[26] = {0}, beta2[26] = {0}, counter = 0;
  char str[101], alpha1[27], alpha2[27], a1, a2;
  a1 = 'A';
  a2 = 'a';
  for (i = 0; i < 27; i++) {
    alpha1[i] = a1;
    a1++;
    alpha2[i] = a2;
    a2++;
  }
  scanf("%d", &n);
  scanf("%s", str);
  for (i = 0; i < n; i++) {
    for (j = 0; j < 27; j++) {
      if (str[i] == 'I') {
        beta1[8] = 1;
        beta2[8] = 1;
      } else if (str[i] == alpha1[j - 1]) {
        beta1[j - 1] = 1;
        beta2[j - 1] = 1;
      } else if (str[i] == 'i') {
        beta2[8] = 1;
        beta1[8] = 1;
      } else if (str[i] == alpha2[j - 1]) {
        beta2[j - 1] = 1;
        beta1[j - 1] = 1;
      }
    }
  }
  for (j = 0; j < 27; j++) {
    if (beta1[j] == 0) counter++;
    if (beta2[j] == 0) counter++;
  }
  if (counter == 0)
    printf("YES");
  else
    printf("NO");
  return 0;
}
