AT_past20_e リンゴ集め

Apples are dropping onto a number line. $ A_i $ apples will drop onto the coordinate $ i $ for each $ i=1,2,\ldots,N $ ; no other apples will drop. You have a basket of width $ W $ . You may freely choose an integer $ L $ to place the basket, aligning its left end at $ L $ , so that it collects apples falling onto the coordinates between $ L $ and $ L+W-1 $ , inclusive. At most how many apples can you collect?

The input is given from Standard Input in the following format: > $ N $ $ W $ $ A_1 $ $ A_2 $ $ \ldots $ $ A_N $

Print the answer.

### Sample Explanation 1 If you set $ L=3 $ , the basket collects $ 4+1+5=10 $ apples falling onto coordinates $ 3,4,5 $ . This is the maximum. ### Constraints - $ 1 \leq W \leq N \leq 10^6 $ - $ 0 \leq A_i \leq 10^3 $ - All input values are integers.