#include <bits/stdc++.h>
using namespace std;
string s;
bool alphabet[40];
int main() {
  int n;
  cin >> n;
  cin >> s;
  for (int i = 0; i < s.size(); i++) s[i] = tolower(s[i]);
  for (int i = 0; i < s.size(); i++) {
    alphabet[s[i] - 'a' + 1] = true;
  }
  for (int i = 1; i <= 26; i++) {
    if (alphabet[i] == false) {
      cout << "NO" << endl;
      return 0;
    }
  }
  cout << "YES" << endl;
}
