#pragma GCC optimize("Ofast")
#include<iostream>
#include<stdio.h>
#include<algorithm>
#include<vector>
#include<string.h>
#include<math.h>
#include<map>
#include<iomanip>
#include<queue>

const long long INFL = 1e17+7;
const long long INFI = 1e9+7;
const long long MOD = 1e9+7;
const double EXP = 1e-8;
const double PI=acos(-1);

using namespace std;

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);
	
	string s;
	cin >> s;
	vector<int> a(26,0);
	
	for(int i=0;i<s.size();i++){
		a[s[i]-'A']++;
	}
	
	for(int i=0;i<26;i++){
		if(a[i]>1){
			cout << "NO" << endl;
			return 0;
		}
	}
	cout << "YES" << endl;
	return 0;
}