#include <iostream>

using namespace std;

int main(void){
    int flag[27]={0};
    char str[11];
    
    cin >> str;
    int i=0;
    while(str[i] != '\0'){
        if(++flag[str[i]-'A'] == 2){
            cout << "NO" << endl;
            return 0;
        }
        i++;
    }
    cout << "YES" << endl;
    
    return 0;
}