Devil's Hell deLivery

Devil's Hell deLivery company delivers literally everything: boxes, packages, packets, datagrams et cetera.

The delivery process from city A to city B works as follows. There are $N$ trucks and $K$ items. The capacity of truck number $i$ is $c_i$. The weight of item number $j$ is $w_j$. The trucks make one or more delivery steps.

During one step, some items are loaded into some trucks. Items cannot be split. The total weight of the items assigned to each truck must not exceed that truck's capacity. All trucks depart simultaneously.

At the end of each step, all trucks return to the place where they started. If any items are left, another step is performed.

Distribute the items among steps and trucks so that the number of steps is minimized.

The input contains up to a hundred test cases.

Each test case starts with a line containing two integers $N$ and $K$ ($1 \le N \le 5$, $1 \le K \le 9$): the number of trucks and the number of items. The next line contains $N$ integers $c_1, \ldots, c_N$ ($1 \le c_i \le 10^8$): the capacities of the trucks. The next line contains $K$ integers $w_1, \ldots, w_K$ ($1 \le w_i \le 10^8$): the weights of the items.

For each test case, if the delivery is impossible, write a single line containing the integer $-1$.

Otherwise, write a line containing a single integer $S$: the number of steps required. This number must be minimized. Then write $S$ lines describing the steps. Each step description starts with an integer $I_i$, the number of items delivered during the step, followed by $I_i$ pairs $a_j$ $b_j$. Each pair means that item $a_j$ is assigned to truck $b_j$.

If more than one optimal answer exists, write any one of them.