#include <bits/stdc++.h>
int main() {
  int x, i, j[125] = {0}, y, count;
  scanf("%d", &x);
  char word[x];
  scanf("%s", word);
  y = strlen(word);
  if (y < 26)
    printf("NO");
  else {
    for (i = 0; i < y; i++) {
      if ((word[i] >= 'A' && word[i] <= 'Z') ||
          (word[i] >= 'a' && word[i] <= 'z')) {
        if (word[i] >= 'A' && word[i] <= 'Z') {
          word[i] = word[i] + 32;
          j[word[i]] = 1;
        } else
          j[word[i]] = 1;
      }
    }
    count = 0;
    for (i = 65; i < 125; i++) {
      if (j[i] != 0) {
        ++count;
      }
    }
    if (count == 26)
      printf("YES");
    else
      printf("No");
  }
  return 0;
}
