#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  string s;
  bool used[256];
  memset(used, false, sizeof(used));
  cin >> n;
  cin >> s;
  for (int i = 0; i < n; i++) {
    used[toupper(s[i])] = true;
  }
  for (char c = 'A'; c <= 'Z'; c++) {
    if (!used[c]) {
      puts("NO");
      return 0;
    }
  }
  cout << "YES\n";
  return 0;
}
