import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc=new Scanner(System.in);
		int c[][]=new int[3][3];
		for(int i=0;i<3;i++){
			for(int j=0;j<3;j++){
				c[i][j]=sc.nextInt();
			}
		}
		int s1=c[0][1]+c[0][2]+c[1][2];
		int s2=c[1][0]+c[2][0]+c[2][1];
		int s=c[0][0]+c[1][1]+c[2][2];
		if(s1+s2==2*s){
			System.out.println("Yes");
		}else{
			System.out.println("No");
		}
	}

}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz