#include <iostream>
using namespace std;
int main(){
    char cnt[26]={0};
    bool TF=true;
    string S;
    cin >> S;
    for(int p=0;p<S.size();p++){
        if(cnt[S[p]-'A']++>0)TF=false;
    }
    if(TF)cout << "YES" << endl;
    else cout << "NO" << endl;
    return 0;
}