#include <bits/stdc++.h>
using namespace std;
map<char, int> m;
int main() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  for (int i = 0; i < s.size(); ++i) m[(s[i] >= 'a' ? s[i] - 32 : s[i])]++;
  for (char c = 'A'; c <= 'Z'; c++) {
    if (m[c] == 0) {
      cout << "NO" << endl;
      return 0;
    }
  }
  cout << "YES" << endl;
  return 0;
}
