#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <wait.h>
#include <signal.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <sys/shm.h>
#include <limits.h>

long long mult;
pid_t gen0, gen1, gen2;
int fd[2];

void
hndlr_end(int sig)
{
    signal(SIGUSR1, hndlr_end);

    printf("hndlr_end\n");

    if (!gen2 && !gen1) {
        exit(0);
    } else {
        wait(NULL);
        exit(0);
    }
}

void
hndlr(int sig)
{
    signal(SIGUSR1, hndlr);

    printf("hndlr\n");
    printf("gen0= %d, gen1 = %d, gen2 = %d\n", gen0, gen1, gen2);

    long long elm;

    if (!gen2 && !gen1) {   //grandson
        read(fd[0], &elm, sizeof(elm));
        printf("%lld\n", elm);
        elm *= mult;
        write(fd[1], &elm, sizeof(elm));
        kill(gen0, SIGUSR1);
    } else if (!gen1) {   //son
        if (scanf("%lld", &elm) != 1) {
            printf("END\n");
            signal(SIGUSR1, hndlr_end);
            kill(gen2, SIGUSR1/*!SIGTERM*/);
            wait(NULL);
            printf("*********\n");
            kill(gen0, SIGUSR1);
            exit(0);
        }
        write(fd[1], &elm, sizeof(elm));
        kill(gen2, SIGUSR1);
    } else {
        read(fd[0], &elm, sizeof(elm));
        printf("%lld\n", elm);
        kill(gen1, SIGUSR1);
    }
}

int
main(int argc, char **argv)
{
    signal(SIGUSR1, hndlr);

    setbuf(stdin, NULL);
    setbuf(stdout, NULL);

    sscanf(argv[1], "%lld", &mult);

    pipe(fd);

    gen0 = getpid();
    gen1 = fork();
    if (gen1 < 0) {
        _exit(0);
    } else if (!gen1) {
        gen2 = fork();
        if (gen2 < 0) {
            _exit(0);
        } else if (!gen2) {
            kill(getppid(), SIGUSR1);
            while (1) {
                pause();
            }
        } else {
            while (1) {
                pause();
            }
        }
    } else {
        while (1) {
            pause();
        }
    }
}