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