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