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

#define N 20

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

    int my_id, num_procs;
    int i,j;
    int rem, num_local_row;
    int *matrix;
    int proc_up, proc_down;
    MPI_Status  status1, status2;

    MPI_Init(&argc,&argv);
    MPI_Comm_rank(MPI_COMM_WORLD,&my_id);
    MPI_Comm_size(MPI_COMM_WORLD,&num_procs);

    /*  numer of rows for each mpi task */

    rem= N % num_procs;
    num_local_row = (N - rem)/num_procs;

    if(my_id < rem) num_local_row = num_local_row+1;

    matrix = (int*) malloc(((num_local_row+2)*N)*sizeof(int));

    /* inizialization of the local matrix */
    for(i=0; i<num_local_row+2 ;i++){
      for(j=0; j<N; j++){
        matrix[i*N+j] = my_id ;
      }
    }
    // Compute proc_up, proc_down
    ...


    /* send receive of the ghost reagions */
    // Use MPI_Sendrecv for communications
	...

    /* check printings */
    printf("\n ");

    printf("my_id, %d, row from above: ", my_id);
    for(i=0;i<N;i++){
      printf("%d \t", matrix[i]);
    }
    printf("\n ");

    printf("my_id, %d, row from bottom: ", my_id);
    for(i=N*(num_local_row+1);i<N*(num_local_row+1)+N;i++){
      printf("%d \t", matrix[i]);
    }
    printf("\n ");

    free(matrix);
	// Finalize
	...
	
    return 0;
  }