PROGRAMMING:Matrix a times b

Given two matrices $$a $$and $$B $$, you are asked to calculate their product matrix $$AB $. It should be noted that only matrices with scale matching can be multiplied. That is, if $$a $$has $$R_ A $$line, $$C_ A $$column, $$B $$has $$R_ B $$line, $$C_ B $$column, there is only $$C_ A $$and $$R_ When B $$is equal, two matrices can be multiplied.
###Input format:
Input gives two matrices $$a $$and $$B $$. For each matrix, the number of rows $$R $$and the number of columns $$C $$are given in a row first, and then the number of rows $$R $$is given in a row. Each row is given $$C $$integers separated by one space, and there are no extra spaces at the beginning and end of the row. The input guarantees that the $$R $$and $$C $$of the two matrices are positive numbers, and the absolute values of all integers do not exceed 100.
###Output format:
If the scales of the two input matrices are matched, then the product matrix $$AB $$is output according to the input format, otherwise ` error: CA= RB ', where' Ca 'is the number of columns of $$a $, and' RB 'is the number of rows of $$B $.
###Input sample 1:
```in
2 3
1 2 3
4 5 6
3 4
7 8 9 0
-1 -2 -3 -4
5 6 7 8
```
###Output sample 1:
```out
2 4
20 22 24 16
53 58 63 28
```
###Input example 2:
```
3 2
38 26
43 -5
0 17
3 2
-11 57
99 68
81 72
```
###Output example 2:
```
Error: 2 != three
```






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