#include <bits/stdc++.h>
using namespace std;
int main() {
  int c;
  string a;
  cin >> c;
  cin >> a;
  int ht[26] = {0}, t, ans = 0;
  for (int i = 0; i < c; i++) {
    t = a[i];
    if (t >= 97 && t <= 122) t -= 97;
    if (t >= 65 && t <= 90) t -= 65;
    ht[t]++;
  }
  for (int i = 0; i < 26; i++) {
    if (ht[i] > 0) ans++;
  }
  if (ans == 26)
    cout << "YES"
         << "\n";
  else
    cout << "NO"
         << "\n";
  return 0;
}
