#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  string s;
  cin >> n >> s;
  char a = 'A';
  for (int i = 0; i < n; i++) {
    s[i] = toupper(s[i]);
  }
  if (n >= 26) {
    for (int i = 0; i < 26; i++) {
      if (s.find(a) != -1) {
        a++;
      } else {
        cout << "NO";
        return 0;
      }
    }
    cout << "YES";
  } else {
    cout << "NO";
  }
  return 0;
}
