#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  int appears[26] = {0};
  for (char c : s) {
    if (c <= 'Z')
      appears[c - 'A'] = 1;
    else if (c <= 'z')
      appears[c - 'a'] = 1;
  }
  bool pangram = true;
  for (int i = 0; i < 26; ++i) {
    if (appears[i] == 0) {
      pangram = false;
      break;
    }
  }
  if (pangram)
    cout << "YES\n";
  else
    cout << "NO\n";
  return 0;
}
