#include <bits/stdc++.h>
using namespace std;
long long int cnt;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(NULL);
  cout.tie(NULL);
  int n;
  cin >> n;
  string s;
  cin >> s;
  set<char> ans;
  for (int i = 0; i < s.size(); i++) {
    if (s[i] < 'a') s[i] += 32;
    ans.insert(s[i]);
  }
  if (ans.size() == 26)
    cout << "YES";
  else
    cout << "NO";
  return 0;
}
