Barr the bear is bored. He grabs the nearest piece of paper and scribbles an equation:

*a*_{1} - *a*_{2} + *a*_{3} - *a*_{4} + ... + *a*_{N-1} - *a*_{N} = *x*.

Naturally, *N* has to be even for the equation to hold. Then he takes his trusty random number generator and starts generating random integers. He records the first *K* such integers on a card, the next *K* integers on another card, and so on, until he has recorded *K***N* integers on *N* cards.

He decides to align the cards nicely with the variables, each card to 1 variable. Then he picks a number from each card to be the value of the respective variable in the equation. He wonders, how can he do this such that the value *x* is minimised?

He does not wonder for long. After 10 seconds, he realises, "This is trivial." Can you figure out his trivial solution?

## Input

The first line contains integers *N* (2 ≤ *N* ≤ 75,000, *N* is even) and *K* (1 ≤ *K* ≤ 100). The following *N* lines contains *K* space-separated integers each; the *j*^{th} integer of the *i*^{th} of these lines is an integer *a*_{i,j} that represents the *j*^{th} integer on the *i*^{th} card (1 ≤ *i* ≤ *N*, 1 ≤ *j* ≤ *K*, -2000 ≤ *a*_{i,j} ≤ 2000).
## Output

The first line should contain a single integer: the minimum possible *x* assuming that you align the cards and choose the numbers optimally.
## Sample Input 1

4 2
-2 3
-5 -3
3 6
-10 7

## Sample Output 1

-24

## Explanation for Sample Output 1

A possible optimal solution is to align the the 2nd card with *a*_{1}, the 1st card with *a*_{2}, the 4th card with *a*_{3} and the 3rd card with *a*_{4}. Then pick integers -5, 3, -10, 6 respectively.

*x* = (-5) - 3 + (-10) - 6 = -24