今日興趣新聞：

NASA 研製最強推進器，加速度可達每秒 40 公裡，飛火星全靠它

鏈接：https://mbd.baidu.com/newspage/data/landingsuper?context=%7B"nid"%3A"news_11707429683828231737"%7D&n_type=0&p_from=1

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The heat during the last few days has been really intense. Scientists from all over the Berland study how the temperatures and weather change, and they claim that this summer is abnormally hot. But any scientific claim sounds a lot more reasonable if there are some numbers involved, so they have decided to actually calculate some value which would represent how high the temperatures are.

Mathematicians of Berland State University came up with a special heat intensity value. This value is calculated as follows:

Suppose we want to analyze the segment of nn consecutive days. We have measured the temperatures during these nn days; the temperature during ii-th day equals aiai.

We denote the average temperature of a segment of some consecutive days as the arithmetic mean of the temperature measures during this segment of days. So, if we want to analyze the average temperature from day xx to day yy, we calculate it as ∑i=xyaiy−x+1∑i=xyaiy−x+1 (note that division is performed without any rounding). The heat intensity value is the maximum of average temperatures over all segments of not less than kkconsecutive days. For example, if analyzing the measures [3,4,1,2][3,4,1,2] and k=3k=3, we are interested in segments [3,4,1][3,4,1], [4,1,2][4,1,2] and [3,4,1,2][3,4,1,2] (we want to find the maximum value of average temperature over these segments).

You have been hired by Berland State University to write a program that would compute the heat intensity value of a given period of days. Are you up to this task?

Input

The first line contains two integers nn and kk (1≤k≤n≤50001≤k≤n≤5000) — the number of days in the given period, and the minimum number of days in a segment we consider when calculating heat intensity value, respectively.

The second line contains nn integers a1a1, a2a2, ..., anan (1≤ai≤50001≤ai≤5000) — the temperature measures during given nn days.

Output

Print one real number — the heat intensity value, i. e., the maximum of average temperatures over all segments of not less than kkconsecutive days.

Your answer will be considered correct if the following condition holds: |res−res0|<10−6|res−res0|<10−6, where resres is your answer, and res0res0 is the answer given by the jury's solution.

input

4 3
3 4 1 2

output

2.666666666666667

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（一） 題目分析：

　　　　正常div3難度題型，難度處理可能是在求和統計上，題目大概含義就是：

　　　　求n個數中至少連續k個數的平均值的最大值，如：n=4,k=3   給定的n個數是3 4 1 2，則求[3,4,1],[4,1,2],[3,4,1,2]三個區間的平均值的最大值。

　　　　我用的方法比較簡單，就是簡單的取值求和，今天下午打完題之後這道題還特地搜了一下，發現還有其他的解法：首碼和 /  尺縮

（二）AC代碼：

　　　　因為代碼比較簡單，依舊不分塊了~

#include<stdio.h>
#define max(a,b) (a>b) ? a : b
using namespace std;
int n,k,sum;
int temp[5001];
double ans,all;
int main()
{
    scanf("%d%d",&n,&k);
    ans = 0;
    for(int i = 1;i<=n;i++) scanf("%d",&temp[i]);

    for(int i = 1;i<=n;++i)
    {
        sum = 0;
        for(int j = i;j<=n;++j)
        {
            sum+= temp[j];
            if (j - i + 1 >= k) 
            {
                all = sum * 1.0 / (j - i + 1);
                if(all>ans) ans = all;
            }
        }
    }
    printf("%.15f\n",ans);
    return 0;
}

（三）AC截圖：

（四）解後分析：

　　貢獻一個隊內牛逼師兄高效率的代碼：

　　備註一下：首碼和