#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <semaphore.h>

#define NUM_THREADS 5

void *s_one(void*);
void *s_two(void*);
void *s_three(void*);
void *s_four(void*);
void *s_five(void*);

sem_t s2;
sem_t s4;
sem_t mainwait;
sem_t s5;

int S;
int A=1;
int B=2;
int C=3;
int D=4;


int main()
{
    //pthread_t thread_id[NUM_THREADS];
    sem_init(&s2, 0, 1);
    sem_init(&s4, 0, 0);
    sem_init(&s5, 0, 1);
    sem_init(&mainwait, 0, 1);

    pthread_t thread1;
    pthread_t thread2;
    pthread_t thread3;
    pthread_t thread4;
    pthread_t thread5;

    pthread_create(thread1,NULL,s_one,NULL);
    pthread_create(thread2,NULL,s_two,NULL);
    pthread_create(thread3,NULL,s_three,NULL);
    pthread_create(thread4,NULL,s_four,NULL);
    pthread_create(thread5,NULL,s_five,NULL);

    sem_wait(&mainwait);

    return 0;
}


void *s_one(void* arg)
{
    printf("s_one");
    A = B+C;
    sem_post(&s2);
}

void *s_two(void* arg)
{
    sem_wait(&s2);
    printf("s_two");
    C = B * D;
    sem_post(&s4);
}

void *s_three(void* arg)
{
    printf("s_three");
    S = 0;
    sem_post(&s4);
}

void *s_four(void* arg)
{
    sem_wait(&s4);
    int j;
    int X=0;

    for(j=A; j<=100; j++)
    {
        X = j + 1;
        S = S + (X+1); //(X+1) can be replaced by j+1.
    }
    sem_post(&s5);
}

void *s_five(void* arg)
{
    sem_wait(&s5);
    if(S > 1000)
        C = C * 2;
    sem_post(&mainwait);
}