#include <bits/stdc++.h>
using namespace std;
const long long int M = 1000003;
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  long long int n;
  cin >> n;
  string s;
  cin >> s;
  set<char> st;
  for (long long int i = 0; i < n; i++) {
    char temp = s[i];
    if (temp >= 'A' && temp <= 'Z') temp += 32;
    st.insert(temp);
  }
  for (char ch = 'a'; ch <= 'z'; ch++) {
    if (st.count(ch) == 0) {
      cout << "NO"
           << "\n";
      return 0;
    }
  }
  cout << "YES"
       << "\n";
}
