import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;

public class No908 {
  public static void main(String[] args) throws IOException{
    String inputValue = new BufferedReader(new InputStreamReader(System.in)).readLine();
    boolean strFlag = true;

    for(int i=0;i < inputValue.length();i++){

      if((i+1) % 2 == 0 && inputValue.charAt(i) != ' '
         || (i+1) % 2 != 0 && inputValue.charAt(i) == ' '){
          strFlag = false;
          break;
      }
    }
      System.out.println(strFlag ? "YES":"NO");
  }
}