#include <bits/stdc++.h>
using namespace std;
int main() {
  int i, cnt = 0, n;
  cin >> n;
  char s[n];
  cin >> s;
  for (i = 0; i < n; i++) {
    if (s[i] >= 65 && s[i] <= 90) {
      s[i] = 97 + s[i] - 65;
    }
  }
  sort(s, s + n);
  for (i = 0; i < n; i++) {
    if (s[i] != s[i + 1]) {
      cnt++;
    }
  }
  if (cnt == 26)
    cout << "YES" << endl;
  else
    cout << "NO" << endl;
  return 0;
}
