#include <bits/stdc++.h>   using namespace std;   int main() {     int n;     cin >> n;     string str;     cin >> str;     set<char> a;     for (int i = 0; i < n; i++) {       a.insert(tolower(str[i]));     }     if (a.size() == 26) {       cout <<  YES  << endl;     } else {       cout <<  NO  << endl;     }     return 0;   }   