#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, c = 0;
  string s = "cBa", l = "abcdefghijklmnopqrstuvwxyz";
  cin >> n >> s;
  for (int i = 0; i < 26; i++) {
    for (int j = 0; j < n; j++) {
      if (tolower(s[j]) == l[i]) {
        c++;
        break;
      }
    }
  }
  if (c == 26)
    cout << "YES";
  else
    cout << "NO";
  return 0;
}
