#include <bits/stdc++.h>
int main() {
  char s[128];
  char c;
  int ss[256] = {0};
  int n;
  scanf("%d", &n);
  int i;
  getchar();
  for (i = 0; i < n; i++) {
    c = getchar();
    if (c >= 'a' && c <= 'z') c -= 32;
    ss[c]++;
  }
  for (i = 'A'; i <= 'Z'; i++)
    if (ss[i] == 0) break;
  if (i == 'Z' + 1)
    puts("YES");
  else
    puts("NO");
}
