Sliding Window Average

Given an integer array and a positive window length, output the average of every contiguous window; if the window length exceeds the array length, the result is empty.

输入格式

This site's input: the first line contains n and w (0≤n≤50000, 1≤w≤100000), and the second line contains n integers (−10⁹..10⁹).

输出格式

The first line is the number of results. If it is greater than 0, the second line gives the averages in window order, separated by spaces; for an empty result, output only 0. Each value may have an absolute or relative error of at most 10⁻⁵, and NaN or Infinity must not be output.

样例 1

输入：

9 7
1 2 3 4 5 6 7 8 9

输出：

3
4 5 6

样例 2

输入：

3 3
1 0 0

输出：

1
0.33333333333333333333333333333333333333333333333333

样例 3

输入：

2 3
1 2

输出：

0

样例说明

Example 1: the three windows sum to 28, 35, and 42; dividing by 7 gives 4.000000, 5.000000, and 6.000000.

Example 2: the only window's average is 1/3, which is 0.333333 to six decimal places.

Example 3: the window length 3 exceeds the array length 2, so there is no complete window, and the output count is 0.