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 <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<ll, ll> P;

#define fi first
#define se second
#define repl(i,a,b) for(ll i=(ll)(a);i<(ll)(b);i++)
#define rep(i,n) repl(i,0,n)
#define all(x) (x).begin(),(x).end()
#define dbg(x) cout<<#x"="<<x<<endl
#define mmax(x,y) (x>y?x:y)
#define mmin(x,y) (x<y?x:y)
#define maxch(x,y) x=mmax(x,y)
#define minch(x,y) x=mmin(x,y)
#define uni(x) x.erase(unique(all(x)),x.end())
#define exist(x,y) (find(all(x),y)!=x.end())
#define bcnt __builtin_popcount

#define INF 1e16
#define mod 1000000007

ll n,m;
ll a[505];
ll sum[505];
double dp[505][505];

int main(){
  cin>>n>>m;
  m=n-m;
  rep(i,n)cin>>a[i];
  rep(i,n)sum[i+1]=sum[i]+a[i];
  rep(i,505)rep(j,505)dp[i][j]=-INF;
  dp[0][0]=0;
  rep(i,n)rep(j,m+1){
    ll sum=0;
    repl(k,i,n){
      sum+=a[k];
      ll num=k-i+1;
      maxch(dp[k+1][j+num-1],dp[i][j]+(double)sum/(double)num);
    }
  }
  printf("%.10f\n", dp[n][m]);
  return 0;
}

