#include <bits/stdc++.h>
using namespace std;
typedef long long  ll;
typedef vector<int> VI;
typedef vector<ll> VLL;
#define rep(i,n) for(int i=0; i<(int)(n); i++)

int main(){
    string s;
    cin >> s;

    map<char, int> m;

    char a = 'A';
    rep(i,26){
        m[a+i] = 0;
    }

    rep(i,s.size()){
        if(m[s[i]] != 0){
            cout << "NO" << endl;
            return 0;
        }else{
          m[s[i]] = 1;
        } 
    }

    cout << "YES" << endl;
    return 0;

}