#include <bits/stdc++.h>
using namespace std;
int main(int argc, char const *argv[]) {
  int n;
  cin >> n;
  string s;
  cin >> s;
  set<char> mp;
  for (auto x : s) {
    char t = tolower(x);
    mp.insert(t);
  }
  if (mp.size() == 26)
    cout << "YES";
  else
    cout << "NO";
  return 0;
}
