#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  bool a[26], b[26];
  for (int i = 0; i < 26; i++) a[i] = false;
  for (int i = 0; i < 26; i++) b[i] = false;
  for (int i = 0; i < n; i++) {
    if (s[i] <= 'z' && s[i] >= 'a') a[s[i] - 'a'] = true;
    if (s[i] <= 'Z' && s[i] >= 'A') b[s[i] - 'A'] = true;
  }
  for (int i = 0; i < 26; i++) {
    if (a[i] == false && b[i] == false) {
      cout << "NO";
      return 0;
    }
  }
  cout << "YES";
  return 0;
}
