#include <bits/stdc++.h>
using namespace std;
int main() {
  int c = 0;
  string str;
  int n;
  cin >> n;
  cin >> str;
  int alphapet[26] = {0};
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < 26; j++) {
      if (str.at(i) == (j + 65) || str.at(i) == (j + 97)) {
        alphapet[j] = 1;
      }
    }
  }
  for (int i = 0; i < 26; i++) {
    if (alphapet[i] == 1) c++;
  }
  if (c >= 26)
    cout << "YES";
  else
    cout << "NO";
  return 0;
}
