#include <bits/stdc++.h>
using namespace std;
int main() {
  char arr[26] = {'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i',
                  'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r',
                  's', 't', 'u', 'v', 'w', 'x', 'y', 'z'};
  int n;
  int counter = 0;
  vector<char> S;
  cin >> n;
  for (int i = 0; i < n; i++) {
    char c;
    cin >> c;
    c = tolower(c);
    S.push_back(c);
  }
  vector<bool> bol;
  for (int j = 0; j < 26; j++) {
    bol.push_back(false);
  }
  for (int i = 0; i < S.size(); i++) {
    for (int j = 0; j < 26; j++) {
      if (S[i] == arr[j]) {
        bol[j] = true;
        break;
      }
    }
  }
  for (int i = 0; i < 26; i++) {
    if (bol[i] == false) {
      cout << "NO" << endl;
      return 0;
    }
  }
  cout << "YES" << endl;
  return 0;
}
