#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  int lol[1000] = {0};
  for (int i = 0; i < n; i++) {
    if (s[i] < 'a') {
      s[i] += 32;
    }
    lol[s[i]]++;
  }
  for (char a = 'a'; a <= 'z'; a++) {
    if (lol[a] == 0) {
      cout << "NO" << endl;
      return 0;
    }
  }
  cout << "YES" << endl;
  return 0;
}
