#include <bits/stdc++.h>
using namespace std;
int a[26];
char str[105];
int main() {
  int n;
  while (scanf("%d", &n) != EOF) {
    memset(a, 0, sizeof(a));
    scanf("%s", str);
    for (int i = 0; str[i] != '\0'; i++) {
      if (str[i] <= 'z' && str[i] >= 'a')
        a[str[i] - 'a'] = 1;
      else if (str[i] <= 'Z' && str[i] >= 'A')
        a[str[i] - 'A'] = 1;
    }
    int ans = 0;
    for (int i = 0; i < 26; i++) ans += a[i];
    if (ans == 26)
      printf("YES\n");
    else
      printf("NO\n");
  }
  return 0;
}
