#include<iostream>
#include <algorithm>
#include<string>
#include <bitset>
#include <vector>
#include <functional>
#include <climits>
#include <iomanip>
#include <utility>
#include <stack>
#include <queue>
#include <math.h>
#include <iomanip>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
using namespace std;
using ll = long long;
ll n, m;
ll sum = 0;
ll memo[50][50] = {};
void kansuu(ll num, ll visited[10]) {

}
int main()
{
	ll a, b = 0, c = 0, d = 0;
	ll l;
	char C[1000][1000] = {};
	ll h, w, sy, sx, gy, gx;
	queue<int> x, y;
	string s;
	cin >> s;
	ll z[100] = {};
	for (int i = 0; i < s.length(); i++)
	{
		if (z[s[i]-'A']==1)
		{
			cout <<"NO"<< endl;
			return 0;
		}
		else
		{
			z[s[i] - 'A'] = 1;
		}
	}
	cout << "YES" << endl;

	//cout << sum << endl;
	//cout <<  endl;

	return 0;
}
//memcpy(x, visited, sizeof(ll)*n);
//void kansuu(ll num, ll visited[10]) {}
//kansuu(1, zz);