#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, sum = 0;
  string s;
  cin >> n >> s;
  for (int i = 97; i < 123; i++) {
    for (int j = 0; j < n; j++) {
      if (i == tolower(s[j])) {
        sum++;
        break;
      }
    }
    if (sum == 26) break;
  }
  if (sum == 26)
    cout << "YES";
  else
    cout << "NO";
  return 0;
}
