#include <bits/stdc++.h>
using namespace std;
int main() {
  char a;
  int n, count[26] = {0};
  bool full = true;
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> a;
    if (a >= 'A' && a <= 'Z') a += 32;
    if (a >= 'a' && a <= 'z') count[a - 97]++;
  }
  for (int i = 0; i < 26; i++) {
    if (count[i] == 0) {
      full = false;
      break;
    }
  }
  if (!full)
    cout << "NO" << endl;
  else
    cout << "YES" << endl;
  return 0;
}
