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

int main( int argc, char *argv[])   /* greetings_comm */
{
    int my_rank, np, sender, recipient, tag, ln, ierr;
    char name[100], message[100]=", greetings from ";
    MPI_Status status;

    ierr = MPI_Init(&argc,&argv);
    ierr = MPI_Comm_rank(MPI_COMM_WORLD,&my_rank);
    ierr = MPI_Comm_size(MPI_COMM_WORLD,&np);

    sender = my_rank - 1;  recipient = my_rank + 1;
    if ( my_rank == 0 ) {
      printf("What's your name?\n");
      scanf("%s",name);
      ln = strlen(name);
    }
    
    if ( sender >= 0 ) {
      tag = 0;
      ierr = MPI_Recv(&ln, 1, MPI_INT, sender, tag, MPI_COMM_WORLD, &status);
      tag = 1;
      ierr = MPI_Recv(name, ln, MPI_CHAR, sender, tag, MPI_COMM_WORLD, &status);
    }
    
    
    if ( recipient < np ) {
      tag = 0;
      ierr =  MPI_Send(&ln, 1, MPI_INT, recipient, tag, MPI_COMM_WORLD);
      tag = 1;
      ierr =  MPI_Send(name, ln, MPI_CHAR, recipient, tag, MPI_COMM_WORLD);
    }   
   
    name[ln]='\0';
    printf("Hi %s %s %d\n",name,message,my_rank);


    MPI_Finalize();

    return 0;
}