#include <bits/stdc++.h>
int main() {
  int a[26];
  char s[120];
  int n;
  while (~scanf("%d", &n)) {
    int flag;
    memset(a, 0, sizeof(a));
    scanf("%s", s);
    for (int i = 0; i < n; i++) {
      if (s[i] >= 'A' && s[i] <= 'Z') {
        s[i] = s[i] - 'A' + 'a';
      }
      a[s[i] - 'a'] += 1;
    }
    for (flag = 0; flag < 26; flag++) {
      if (a[flag] == 0) break;
    }
    if (flag == 26)
      printf("YES\n");
    else
      printf("NO\n");
  }
  return 0;
}
