import java.util.*;

public class Main {
	public static void main (String[] args) {
		Scanner sc = new Scanner(System.in);
		char[] arr = sc.nextLine().toCharArray();
		for (int i = 0; i < arr.length; i++) {
		    if (i % 2 == 0) {
		        if (arr[i] < 'a' || arr[i] > 'z') {
		            System.out.println("No");
		            return;
		        }
		    } else {
		        if (arr[i] != ' ') {
		            System.out.println("No");
		            return;
		        }
		    }
		}
		System.out.println("Yes");
	}
}