#include <algorithm>
#include <iostream>
#include <functional>
#include <map>
#include <set>
#include <string>
#include <vector>


using namespace std;

using hint32 = int32_t;
using hint64 = int64_t;
using huint32 = uint32_t;
using huint64 = uint64_t;
using hint = hint32;
using huint = huint32;


#define hrep( i, n )		for( hint i = 0; i < ( hint )( n ); ++i )
#define hrepr( i, n )		for( hint i = ( hint )( n ); i >= 0; --i)
#define hfor( i, a, n )		for( hint i = ( hint )( a ); i < ( hint )( n ); ++i )
#define hforr( i, a, n )	for( hint i = ( hint )( n ); i >= ( hint )( a ); --i)


#define all(x)	(x).begin(),(x).end()


#define dump(x)			std::cout << #x << " = " << x << "\n";
#define hout(x)			std::cout << x << "\n";
#define hout2(x,y)		std::cout << x << "," << y << "\n";
#define hout3(x,y,z)	std::cout << x << "," << y << "," << z << "\n";

#define ini	std::cin.tie(0);std::ios::sync_with_stdio(false)



int main()
{
	ini;

	string s;
	cin >> s;
	int tmp[27] = { 0 };
	hrep(i, s.size())
	{
		tmp[s[i]-'A']++;
		if (tmp[s[i] - 'A'] > 1)
		{
			hout("NO");
			return 0;
		}
	}
	hout("YES");

	return 0;
}