#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  int a[26];
  for (int i = 0; i < 26; i++) {
    a[i] = 0;
  }
  for (int i = 0; i < n; i++) {
    if (s[i] < 97) s[i] += 32;
    a[s[i] - 97]++;
  }
  for (int i = 0; i < 26; i++)
    if (a[i] == 0) {
      cout << "NO";
      return 0;
    }
  cout << "YES";
  return 0;
}
