Best stretch of sales

Problem

A shop records its sales for n days. Management wants the largest total over k days in a row. Print that total.

Example

Input

6 3
4 2 7 1 3 6

Output

The days 4 2 7 add up to 13, the best of all stretches.

Try the problem first. Open one hint at a time.

Hint 1

Add the first k values once, then move one day at a time.

Hint 2

Each move adds the new day and removes the day that left.

Write your Python code, run it on the examples and submit it to hidden tests.