#include <bits/stdc++.h>   using namespace std;   int freq[27];   char sent[101];   int main() {     int n;     scanf( %d , &n);     scanf( %s , sent);     while (n--) {       if (isupper(sent[n])) sent[n] = tolower(sent[n]);       freq[sent[n] -  a ]++;     }     for (int i = 0; i < 26; i++)       if (!freq[i]) {         printf( NO n );         return 0;       }     printf( YES n );     return 0;   }   