#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, i, j, cn = 0;
  cin >> n;
  char b[26] = {'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 a[n];
  cin >> a;
  for (j = 0; j < n; j++)
    if ('a' <= a[j] && a[j] <= 'z') a[j] = a[j] - 'a' + 'A';
  for (i = 0; i < 26; i++) {
    for (j = 0; j < n; j++)
      if (b[i] == a[j]) {
        cn++;
        break;
      }
  }
  if (cn == 26)
    cout << "YES" << endl;
  else
    cout << "NO" << endl;
  return 0;
}
