#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
void filter(int p)
{
	while(1){
		int n;
		ssize_t nb_read = read(0,&n,sizeof(int));
		if (nb_read <= 0)
			break;
		if ((n%p)!=0)
			write(1,&n,sizeof(int));
	}
}

void seq(int n)
{
	for (int i = 2; i <=n; i++)
		write(1,&i,sizeof(int));
}

void chef(void)
{
	while(1){
		int p;
		pid_t f;
		int t[2];
		ssize_t nb_read = read(0,&p,sizeof(int));
		if (nb_read <= 0)
			break;

		printf("new prime %d\n",p);
		pipe(t);
		f = fork();
		if (f == 0){
			close(t[0]);
			dup2(t[1],1);
			close(t[1]);
			filter(p);
			exit(0);
		}
		close(t[1]);
		dup2(t[0],0);
		close(t[0]);
	}
}

int main(int argc, char *argv[])
{
	pid_t p;
	struct sigaction sa = {0};
	sigemptyset(&sa.sa_mask);
	sa.sa_flags = SA_NOCLDWAIT;
	sigaction(SIGCHLD,&sa,NULL);
	int t[2];
	int N = strtol(argv[1],NULL,0);

	pipe(t);
	p = fork();

	if (p == 0){
		close(t[0]);
		dup2(t[1],1);
		close(t[1]);
		seq(N);
		exit(0);
	}
	close(t[1]);
	dup2(t[0],0);
	close(t[0]);
	chef();	
	return 0;
}