#include <bits/stdc++.h>
using namespace std;
char a[100010];
int n, b[26];
int main() {
  while (~scanf("%d", &n)) {
    scanf(" %s", a);
    int k = strlen(a);
    memset(b, 0, sizeof(b));
    for (int i = 0; i < k; i++) {
      if (a[i] >= 'a' && a[i] <= 'z')
        b[a[i] - 'a']++;
      else if (a[i] >= 'A' && a[i] <= 'Z')
        b[a[i] - 'A']++;
    }
    int num = 0;
    for (int i = 0; i < 26; i++)
      if (b[i] > 0) num++;
    if (num == 26)
      puts("YES");
    else
      puts("NO");
  }
}
