#include <bits/stdc++.h>
using namespace std;
int main() {
  int count[26] = {0};
  int n;
  string s;
  cin >> n >> s;
  transform(s.begin(), s.end(), s.begin(), ::tolower);
  for (int i = 0; i < n; i++) {
    count[(int)s[i] - 97]++;
  }
  for (int i = 0; i < 26; i++) {
    if (count[i] == 0) {
      cout << "NO\n";
      return 0;
    }
  }
  cout << "YES\n";
  return 0;
}
