#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  char str[205];
  int num[30];
  while (~scanf("%d", &n)) {
    memset(num, 0, sizeof(num));
    getchar();
    scanf("%s", str);
    if (n < 26) {
      printf("NO\n");
      continue;
    } else {
      int len = strlen(str);
      for (int i = 0; i < len; i++) {
        if (str[i] >= 'A' && str[i] <= 'Z') str[i] += 32;
        num[str[i] - 'a']++;
      }
    }
    int e = 0;
    for (int i = 0; i < 26; i++)
      if (!num[i]) e = 1;
    if (e)
      printf("NO\n");
    else
      printf("YES\n");
  }
  return 0;
}
