#include <bits/stdc++.h>
int main() {
  int n;
  scanf("%d", &n);
  char arr[n + 1];
  scanf("%s", arr);
  int ans[26];
  for (int m = 0; m < 26; m++) ans[m] = 0;
  for (int j = 0; j < n; j++) {
    int k = arr[j];
    if (k > 64 && k < 91)
      ans[k - 65] = 1;
    else
      ans[k - 97] = 1;
  }
  int sum = 0;
  for (int g = 0; g < 26; g++) sum = sum + ans[g];
  if (sum == 26)
    printf("YES\n");
  else
    printf("NO\n");
}
