#include<iostream>
#include<string>
#include<iomanip>
#include<cmath>
#include<vector>
#include<algorithm>
#include<utility>

using namespace std;

#define int long long
#define endl "\n"

constexpr long long INF = (long long)1e18;
constexpr long long MOD = 1'000'000'007; 

struct fast_io {
	fast_io(){
		std::cin.tie(nullptr);
		std::ios::sync_with_stdio(false);
	};
} fio;

bool solve(string s, int b, int e){
	int con[26] = {};
	
	for(int i = b; i <= e; i+=2){
		if(s[i] == ' '){
			return false;
		} else con[s[i] - 'a']++;
		s[i] = 0;
	}
	
	for(int i = 0; i < s.size(); i++){
		if(!s[i]) continue;
		if(s[i] == ' ') continue;
		if(con[s[i]-'a']) return false;
	}
	
	return true;
}


signed main(){
	cout<<fixed<<setprecision(10);
	
	string s;
	
	// cin>>s;
	getline(cin,s);
	
	for(int i = 0; i + 1 < s.size(); i++){
		for(int j = i; j < s.size(); j+=2){
			if(solve(s, i, j)) {
				// cout<<"i = "<<i<<" j = "<<j<<endl;
				cout<<"Yes"<<endl;
				return 0;
			}
		}
	}
	cout<<"NO"<<endl;
	
	
	return 0;
}