#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <stdlib.h>
#include <sys/wait.h>

int a[4]={1,2,3,4};
int main(){
	int p[2];
	pipe(p);
	if (fork()==0){
		a[2]+=a[3];
		write(p[1], &a[2], sizeof(int));
		exit(0);
	}
	a[0]+=a[1];
	read(p[0], &a[2], sizeof(int));
	a[0]+=a[2];
	wait(0);
	printf ("The answer is %d, and it should be 10.\n", a[0]);
	close (p[1]);
	close (p[0]);
	return (0);
}