#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  string s;
  cin >> n >> s;
  set<char> st;
  for (int i = 0; i < s.size(); i++) {
    s[i] = tolower(s[i]);
    st.insert(s[i]);
  }
  if (st.size() == 26)
    cout << "YES" << endl;
  else
    cout << "NO" << endl;
  return 0;
}
