#include<iostream>
#include<vector>
#include<string>
#include<algorithm>
#include<cmath>
#include<queue>
typedef long long ll;
using namespace std;

int main(){
	string s;
	getline(cin, s);
	for (int i = 0; i < s.length(); ++i){
		if ((i + 1) % 2 && !('a' <= s[i] && s[i] <= 'z')){
			cout << "No" << endl;
			exit(0);
		}
		if (!((i + 1) % 2) && s[i] != ' '){
			cout << "No" << endl;
			exit(0);
		}
	}
	cout << "Yes" << endl;
	return 0;
}