#include <mpi.h>
int main (argc, argv)
int argc;
char **argv;
{
  int rcv_tag=MPI_ANY_TAG, from=MPI_ANY_SOURCE;
  int snd_tag=1, rank, size, parent=0, data=1, cnt=1;
  int i, to, sum;
  MPI_Status status;

  /* Initialize MPI */
  MPI_Init (&argc, &argv);

  /* How many processes are in this application */
  MPI_Comm_size (MPI_COMM_WORLD, &size);

  /* Find my rank within this MPI application */
  MPI_Comm_rank (MPI_COMM_WORLD, &rank);

  /* Parent: Sum each child's rank squared value */

  if (rank == parent) {
      for (i = 1, sum = 1; i < size; i++) {
	     MPI_Recv (&data, cnt, MPI_INT, from, rcv_tag, MPI_COMM_WORLD, &status);
	     sum += data;
      }
      printf ("Sum of squares (1-to-%d) is %d\n", size, sum);
  }
  /* Child: Send the parent my rank squared */

  else {
     data = (rank + 1) * (rank + 1);
     MPI_Send (&data, cnt, MPI_INT, parent, snd_tag, MPI_COMM_WORLD);
  }
  MPI_Finalize ();
  exit(0);
}