#include <stdio.h>
#include "mpi.h"

int main(int argc, char *argv[])
{
  /* Processnumber and Number of Procs */
  int myid, numprocs;
  /* Just a state variable */
  MPI_Status status;
  
  /* Initialize a processor */
  MPI_Init(&argc,&argv);
  /* Retrieve it's id and the total amount of procs */
  MPI_Comm_size(MPI_COMM_WORLD, &numprocs);
  MPI_Comm_rank(MPI_COMM_WORLD, &myid);
 
  /* All procs (but the first) wait for a token to come ... */
  if (myid > 0) 
    MPI_Recv( MPI_BOTTOM, 0, MPI_INT, myid - 1, 0, MPI_COMM_WORLD, 
                  &status);

  /* ... then write their id ... */
  printf("Hello World from process %d\n", myid);
  /* ... flush the stdout buffer ... */
  fflush(stdout);

  /* ... and send the token to the next proc (unless self=last) */
  if (myid + 1 < numprocs)
    MPI_Send( MPI_BOTTOM, 0, MPI_INT, myid + 1, 0, MPI_COMM_WORLD);
  
  /* That's all !!! */
  MPI_Finalize();
}