look

if(0 == rank){

        /* Show the number of processors */
        printf("Number of processors is %d\n", size);
        /* Ask size of message */
        printf("Please give an input size in bytes: \n");
        fflush(NULL);
        /* Read the message size */
        scanf("%d", &messageSize);

        if (messageSize > MAXSIZE) {
            printf("Sorry, that's too much memory!\n\n");
            messageSize = 0;
        }

        printf("Message size is %d\n", messageSize);

        for(int i=1;i<size;i++){
            err = MPI_Send(&messageSize,messageSize,MPI_INT,i,tag,MPI_COMM_WORLD);
             if (err != MPI_SUCCESS) {
                printf("Process 0: Error in MPI_Send!\n");
                exit(1);
            }
        }
    } else {
        err = MPI_Recv(&messageSize, messageSize, MPI_INT, 0, tag, MPI_COMM_WORLD, &status);
         if (err != MPI_SUCCESS) {
            printf("Error in MPI_Recv!\n");
            exit(1);
        }          /* Receive a message from any sender */
        source_id = status.MPI_SOURCE;
        printf("Message received from %d size message",source_id,messageSize);
    }