#include <bits/stdc++.h>
int main() {
  int i, n, j, t = 0;
  char s[105], s1[30];
  scanf("%d", &n);
  for (i = 0; i <= n; i++) scanf("%c", &s[i]);
  s1[0] = 'a';
  for (i = 1; i <= n; i++)
    if (s[i] >= 'A' && s[i] <= 'Z') s[i] = s[i] + 32;
  for (i = 0; i <= 25; i++)
    for (j = 1; j <= n; j++) {
      if (s[j] == 'a' + i) {
        t++;
        break;
      }
    }
  if (t == 26)
    printf("YES");
  else
    printf("NO");
  return 0;
}
