#include <bits/stdc++.h>
using namespace std;
int main() {
  map<char, int> ma;
  int p;
  char a, k[1000];
  cin >> p;
  for (int i = 0; i < p; i++) {
    cin >> k[i];
    a = tolower(k[i]);
    ma[a]++;
  }
  if (ma.size() == 26)
    cout << "YES" << endl;
  else
    cout << "NO" << endl;
}
