#include <bits/stdc++.h>
using namespace std;
int main() {
  int i, j, cont = 0, len, n;
  char arr[52] = {'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i',
                  'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r',
                  's', 't', 'u', 'v', 'w', 'x', 'y', 'z'};
  char str1[1000];
  cin >> n;
  cin >> str1;
  for (i = 0; i < n; i++) {
    if (str1[i] >= 65 && str1[i] <= 91) {
      str1[i] = str1[i] + 32;
    }
  }
  for (i = 0; i < n; i++) {
    for (j = 0; j < 26; j++) {
      if (arr[j] == str1[i]) {
        cont = cont + 1;
        arr[j] = ' ';
      }
    }
  }
  if (cont == 26)
    cout << "YES" << endl;
  else
    cout << "NO" << endl;
}
