#include <bits/stdc++.h>
using namespace std;
int main() {
  char b;
  bool arr[26]{};
  int n, c = 0;
  cin >> n;
  if (n < 26) {
    cout << "NO";
    return 0;
  }
  for (int i = 0; i < n; i++) {
    cin >> b;
    if (islower(b)) {
      if (arr[b - 97] == 0) c++;
      arr[b - 97] = 1;
    }
    if (isupper(b)) {
      if (arr[b - 65] == 0) c++;
      arr[b - 65] = 1;
    }
  }
  if (c >= 26) {
    cout << "YES";
    return 0;
  }
  cout << "NO";
  return 0;
}
