#include <bits/stdc++.h>
using namespace std;
int A[26];
int main() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  int cnt = 0;
  for (int i = 0; i < n; i++) s[i] = tolower(s[i]);
  for (int i = 0; i < n; i++) {
    if (!A[s[i] - 'a']) {
      A[s[i] - 'a'] = 1;
      ++cnt;
    }
  }
  if (cnt == 26)
    cout << "YES";
  else
    cout << "NO";
  return 0;
}
