how to use mahout command matrixmult ?

dear everyone :
this is my problem,firstly,i create two matrix files a and b,
a = 1 3 2 b = 3 2
2 3 1 1 5
1 4 5 2 1
then i put them to filesystem.
i use mahout command :mahout seqdirectory change a and b to seq file a1 and b1.
then,use mahout command :mahout matrixmult , a1*b1
it works,but the anser is

Input Path: hdfs://hacluster/user/zzb/c1/part-00000
Key class: class org.apache.hadoop.io.IntWritable Value Class: class org.apache.mahout.math.VectorWritable
Count: 0

where am i wrong?