int size, rank, rc;
    int ers=0, i, k, nNeighbour, sum=0;
    int index[] = {4,5,7,8,11,12,14,15,19,20,22,23,26,27,29,30};
    int edges[] = {1,2,4,8,0,0,3,2,0,5,6,4,4,7,6,0,9,10,12,8,8,11,10,8,13,14,12,12,15,14};
    MPI_Status status;
    rc = MPI_Init (&argc, &argv);
    MPI_Comm comm1, comm2;
    MPI_Comm_rank (MPI_COMM_WORLD, &rank);
    MPI_Comm_size (MPI_COMM_WORLD, &size);

    if(!index || !edges) {
        printf("unable to allocate %d words for index or edges\n", 3*size);
        fflush(stdout);
        MPI_Abort(MPI_COMM_WORLD, 1);
    }

    MPI_Graph_create(MPI_COMM_WORLD, size, index, edges, 0, &comm1);

    srand(rank);
    int a=rand()%100, tmp;
    sum+=a;
    MPI_Graph_neighbors_count(comm1, rank, &nNeighbour);
    int *neighbours;
    neighbours = (int*)malloc(nNeighbour * sizeof(int));
    MPI_Graph_neighbors(comm1, rank, nNeighbour, neighbours);

    if(nNeighbour > 1 && rank != 0) {
        for(i=1; i<nNeighbour; i++) {
            MPI_Recv(&tmp, 1, MPI_INTEGER, neighbours[i], neighbours[i], MPI_COMM_WORLD, &status);
            sum+=tmp;
        }
    }
    if(rank == 0) {
        for(i=0; i<nNeighbour; i++) {
            MPI_Recv(&tmp, 1, MPI_INTEGER, neighbours[i], neighbours[i], MPI_COMM_WORLD, &status);
            sum+=tmp;
        }

        printf("rank %d ha numero %d la somma totale e' %d \n",rank, a, sum);
    }
    else {
        MPI_Send(&sum, 1, MPI_INTEGER, neighbours[0], rank, MPI_COMM_WORLD);
        printf("rank %d ha numero %d la somma parziale e' %d \n", rank, a, sum);
    }

    MPI_Finalize();
}