#include <iostream>
#include<string>
#include<set>
#include<algorithm>
using namespace std;
int main() {
int n;
set<char> c;
cin>>n;
string s;
cin>>s;
transform(s.begin(),s.end(),s.begin(), ::tolower);
for(int i=0;i<s.length();i++){
c.insert(s[i]);
}
// for(int i=0;i<c.size();i++) cout<<c[i]<<endl;
if (c.size()==26) cout<<"YES";
else cout<<"NO";
return 0;
}
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