#include <bits/stdc++.h>
using namespace std;
int cs = 1;
void solve() {
  string str;
  int N, i, s = 0;
  cin >> N;
  cin >> str;
  transform(str.begin(), str.end(), str.begin(), ::toupper);
  sort(str.begin(), str.end());
  for (i = 0; i < N; i++) {
    if (str[i] != str[i + 1]) {
      s++;
    }
  }
  if (s == 26) {
    cout << "YES"
         << "\n";
  } else {
    cout << "NO"
         << "\n";
  }
}
int main() {
  int T = 1;
  while (T--) solve();
  return 0;
}
