problem

AOR Ika got a water tank with a size of $ 1 $ in length and $ N $ in width. The aquarium is tall enough to hold water. The aquarium has $ N-1 $ partitions and is evenly spaced into $ N $ compartments. When water was poured here, the height of the water in each section became $ a_i $.

AOR Ika decided to remove some dividers and reduce the number of compartments to $ M $ or less. When you have removed the dividers, find the maximum sum of the water heights in each compartment.

The thickness of the partition can be ignored.



input

$ N \ M $
$ a_1 \ cdots a_N $

output

Output the maximum value of the total water height of each section in one line. Also, output a line break at the end. It is acceptable if the relative or absolute error is less than or equal to $ 10 ^ {-6} $.

Example

Input

5 3
9 1 2 3 9


Output

20.000000
#include <iostream>
#include <fstream>
#include <string> 
#include <cmath>  
#include <cstdlib>
#include <ctime>
#include <vector>
#include <algorithm>
#include <numeric>
#include <map>
#include <set>
#include <stack>
#include <queue>
#include <deque>
#include <functional>
#include <cctype>

#define BIT(a) (1 << (a))

using namespace std;

long long MOD = 1000000007;


long long mod_pow(long long x, long long n){
    long long res = 1;
    for(int i = 0;i < 60; i++){
        if(n >> i & 1) res = res * x % MOD;
        x = x * x % MOD;
    }
    return res;
}

double dp[505][505];
double a[505];

int main(void){
	// input
	int N, M;
	cin >> N >> M;
	for (int i = 1; i <= N; i++){
		cin >> a[i];
	}
	for (int i = 2; i <= N; i++){
		a[i] += a[i-1];
	}

	// dp init
	for (int i = 0; i < 505; i++){
		for (int j = 0; j < 505; j++){
			dp[i][j] = -1;
		}
	}
	for (int i = 1; i <= N; i++){
		dp[i][1] = a[i]/i;
	}

	for (int i = 2; i <= N; i++){
		for (int len = 1; len < i; len++){
			for (int j = 2; j <= i; j++){
				if (dp[i][j] < dp[i-len][j-1] + (a[i] - a[i-len])/(len)){
					dp[i][j] = dp[i-len][j-1] + (a[i] - a[i-len])/(len);
				}
			}
		}
	}
	printf("%f\n", dp[N][M]);
	return 0;
}


