#include <bits/stdc++.h>
using namespace std;
string s;
int n;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  cin >> n >> s;
  for (int i = 0; i < n; i++) {
    if (s[i] >= 'A' && s[i] <= 'Z') {
      s[i] += 32;
    }
  }
  set<char> a;
  for (int i = 0; i < n; i++) {
    a.insert(s[i]);
  }
  if (a.size() == 26) {
    cout << "YES"
         << "\n";
  } else {
    cout << "NO"
         << "\n";
  }
  return 0;
}
