### Delicious Apples

Time Limit: 3000 ms Memory Limit: 65536 KiB

#### Problem Description

There are n apple trees planted along a cyclic road, which is L metres long. Your storehouse is built at position 0 on that cyclic road.
The ith tree is planted at position xi, clockwise from position 0. There are ai delicious apple(s) on the ith tree.

You only have a basket which can contain at most K apple(s). You are to start from your storehouse, pick all the apples and carry them back to your storehouse using your basket. What is your minimum distance travelled?

1n,k105,ai1,a1+a2+...+an105
1L109
0x[i]L

There are less than 20 huge testcases, and less than 500 small testcases.

#### Input

First line: t, the number of testcases.
Then t testcases follow. In each testcase:
First line contains three integers, L,n,K.
Next n lines, each line contains xi,ai.

#### Output

Output total distance in a line for each testcase.

#### Sample Input

2
10 3 2
2 2
8 2
5 1
10 4 1
2 2
8 2
5 1
0 10000

#### Sample Output

18
26

#### Source

2015 Multi-University Training Contest 2