#include <bits/stdc++.h>
int main(void) {
  char a[105], *p;
  int n, x[27], i, j;
  while (scanf("%d", &n) != EOF) {
    scanf("%s", a);
    if (n < 26)
      printf("NO\n");
    else {
      for (i = 0; i < 27; i++) x[i] = 0;
      for (p = a, i = 0; i < n; p++, i++) {
        if (*p >= 97 && *p <= 122)
          x[*p - 97] = 1;
        else if (*p >= 65 && *p <= 90)
          x[*p - 65] = 1;
      }
      for (j = 0; j < 26; j++) {
        if (x[j] == 0) {
          printf("NO\n");
          break;
        } else if (j == 25)
          printf("YES\n");
      }
    }
  }
  return 0;
}
