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

#include <sys/ipc.h>
#include <sys/sem.h>
#include <sys/stat.h>

int main() {

    char pathname[] = "main.c";
    key_t key;
    if ((key = ftok(pathname, 0)) < 0) { printf("e1\n"); exit(-1); }

    (void)umask(0000);
    int semid;
    if((semid = semget(key, 3, 0666|IPC_CREAT)) < 0) { printf("%de2\n", semid); exit(-1); }

    struct sembuf s[3];
    unsigned short i = 0;
    for (i; i < 3; ++i) {
        s[i].sem_flg = 0;
        s[i].sem_num = i;
    }

    s[0].sem_op = 1;
    s[1].sem_op = 1;
    s[2].sem_op = 0;

    if(semop(semid, s, 3) < 0) { printf("e3\n"); exit(-1); }

    int resfork;
    resfork = fork(); // creating 64 processes, half of which are on the main road and half on the side road
    if (resfork < 0) { printf("ef\n"); exit(-1); }
    else {
    resfork = fork();
    if (resfork < 0) { printf("ef\n"); exit(-1); }
    else {
    resfork = fork();
    if (resfork < 0) { printf("ef\n"); exit(-1); }
    else {
    resfork = fork();
    if (resfork < 0) { printf("ef\n"); exit(-1); }
    else {
    resfork = fork();
    if (resfork < 0) { printf("ef\n"); exit(-1); }
    else {
        resfork = fork();
        if (resfork < 0) { printf("ef\n"); exit(-1); }

        else if (resfork == 0) {
            s[0].sem_num = 0;
            s[0].sem_op = -1;

            s[1].sem_num = 2;
            s[1].sem_op = 1;

            if(semop(semid, s, 2) < 0) { printf("e4\n"); exit(-1); }

            s[0].sem_num = 0;
            s[0].sem_op = 1;

            s[1].sem_num = 1;
            s[1].sem_op = -1;

            if(semop(semid, s, 2) < 0) { printf("e5\n"); exit(-1); }

            s[0].sem_num = 1;
            s[0].sem_op = 1;

            s[1].sem_num = 2;
            s[1].sem_op = -1;

            if(semop(semid, s, 2) < 0) { printf("e6\n"); exit(-1); }
        }

        else if (resfork > 0) {
            s[0].sem_num = 1;
            s[0].sem_op = -1;

            s[1].sem_num = 2;
            s[1].sem_op = 0;

            if(semop(semid, s, 2) < 0) { printf("e7\n"); exit(-1); }

            s[0].sem_num = 2;
            s[0].sem_op = 1;

            if(semop(semid, s, 1) < 0) { printf("e8\n"); exit(-1); }

            s[0].sem_num = 1;
            s[0].sem_op = 1;

            s[1].sem_num = 2;
            s[1].sem_op = -1;

            if(semop(semid, s, 2) < 0) { printf("e9\n"); exit(-1); }
        }

    }}}}}
    return 0;
}