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50398 - Sum of kth Anti-diagonal

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Time limit 2000/4000/4000/4000 ms. Memory limit 65000/65000/65000/65000 Kb.
Prepared by Ibrahim Mesecan.

Sum of kth Anti-diagonal

Question: Antidiagonal of a matrix starts from the lower left corner and goes to the upper right corner. You are given an nXn square matrix. Find the sum of kth anti-diagonal. The third anti-diagonal starts from the third row first element (6). And then, every element is connected to its upper right neigbour (first 9 and then 4).

Input specification
You will be given two integer numbers (n and k) at the beginning where 1 ≤ n ≤ 100 and 1 ≤ k ≤ n. Then, in the following n lines, you will be given n integers, which are between 0 and 1000.

Output specification
Show just one number: the sum of kth diagonal.

 Sample Input   
  5 4
  7 6 4 1 5
  5 9 7 8 7
  6 7 8 7 5
  8 8 0 4 10
  7 5 0 2 0
 Sample Output   
  23


Explanation: 8+7+7+1=23


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