#include<iostream>
#include<set>

using namespace std;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    string str;
    cin >> str;
    set<int> s;
    for (int i = 0; i < (int)str.size(); ++i) {
        s.insert(str[i]);
    }
    if (s.size() == str.size()) cout << "YES" << endl;
    else cout << "NO" << endl;
}