#include <bits/stdc++.h>
using namespace std;
const int MAXN = 110;
int n, book[26];
char a[MAXN];
void solve() {
  if (n < 26) {
    cout << "NO";
    return;
  } else {
    for (int i = 1; i <= n; i++) {
      if (a[i] >= 'a' && a[i] <= 'z') book[a[i] - 'a']++;
      if (a[i] >= 'A' && a[i] <= 'Z') book[a[i] - 'A']++;
    }
    for (int i = 0; i < 26; i++)
      if (!book[i]) {
        cout << "NO";
        return;
      }
  }
  cout << "YES";
}
int main() {
  scanf("%d\n", &n);
  for (int i = 1; i <= n; i++) scanf("%c", &a[i]);
  solve();
}
