#include <bits/stdc++.h>
using namespace std;
void init_ios() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
}
int ile[30], x;
int main() {
  init_ios();
  int n;
  string a;
  cin >> n >> a;
  for (int i = 0; i < n; ++i) {
    if (a[i] >= 'A' && a[i] <= 'Z')
      x = a[i] - 'A';
    else
      x = a[i] - 'a';
    ++ile[x];
  }
  for (int i = 0; i < 26; ++i)
    if (ile[i] == 0) {
      cout << "NO\n";
      return 0;
    }
  cout << "YES\n";
}
