#include <bits/stdc++.h>
int n;
int f[30];
char s[10000];
int main() {
  scanf("%d", &n);
  scanf("%s", s);
  for (int i = 0; i < n; ++i) {
    if (s[i] >= 'a' && s[i] <= 'z')
      f[s[i] - 'a']++;
    else if (s[i] >= 'A' && s[i] <= 'Z')
      f[s[i] - 'A']++;
  }
  for (int i = 0; i < 26; ++i)
    if (f[i] == 0) {
      printf("NO");
      return 0;
    }
  printf("YES");
  return 0;
}
