C++MPI

#include "stdafx.h"
#include <iostream>
#include "mpi.h"
#include <cstdio>
using namespace std;

int main(int argc, char *argv[])
{

    int ierr = MPI_Init(&argc, &argv);
    int numprocs;
    int myid;
    int a;
    int senderID =  0;
    MPI_Comm_size(MPI_COMM_WORLD, &numprocs);
    MPI_Comm_rank(MPI_COMM_WORLD, &myid);

    // process 1-5 receivess the send a, adds or substracts a, and sends it further. process 5 prints all the changes.
    if (myid != 0) {
        MPI_Recv(&a, 1, MPI_INT, MPI_ANY_SOURCE, 1, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
        if (myid == 1 || myid == 2 || myid == 3)
        {
            a += 10;
            senderID = myid;
            MPI_Send(&a, 1, MPI_INT, MPI_ANY_TAG, 0, MPI_COMM_WORLD);
            MPI_Send(&senderID, 1, MPI_INT, 5, 0, MPI_COMM_WORLD);
        }
        else if (myid == 4)
        {
            a -= 50;
            senderID = myid;
            MPI_Send(&a, 1, MPI_INT, MPI_ANY_TAG, 0, MPI_COMM_WORLD);
            MPI_Send(&senderID, 1, MPI_INT, 5, 0, MPI_COMM_WORLD);
        }
        else if (myid == 5)
        {
            while (a >= 0)
            {
                MPI_Recv(&senderID, 1, MPI_INT, 1, 1, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
                if (senderID == 0)
                {
                    cout << "Spausdino" << endl;
                }
                if (1 <= senderID <= 3)
                {
                    cout << "Pridėjo" << endl;
                }
                else
                {
                    cout << "Atėmė" << endl;
                }
            }
        }
    }

    // process P0 initializes a and sends it to all other processes.
    if (myid == 0) {
        a = 100;
        MPI_Send(&a, 1, MPI_INT, MPI_ANY_TAG, 0,MPI_COMM_WORLD);
        MPI_Recv(&a, 1, MPI_INT, MPI_ANY_SOURCE, 1, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
        if (a <= 0)
        MPI_Send(&senderID, 1, MPI_INT, 5, 0, MPI_COMM_WORLD);

    }
    while (a >= 0)
    {
        MPI_Send(&a, 1, MPI_INT, MPI_ANY_TAG, 0, MPI_COMM_WORLD);
    }
    MPI_Finalize();
}