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