#define _DE312BUG
// #include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
// using namespace atcoder;
#define endl "\n"
#define fi first
#define se second
#define all(x) (x).begin(),(x).end() 
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<ld, ld> pld;
typedef vector<int> vi;
typedef vector<pii> vii;
const long double pi = acos(-1.0);
const int INF = 1987654331;
const ll LLINF = 1e18;
const double eps = 1e-9;
template<class T>bool chmax(T& a, const T& b) { if (a < b) { a = b; return 1; } return 0; }
template<class T>bool chmin(T& a, const T& b) { if (b < a) { a = b; return 1; } return 0; }
////////////////////////

// #ifndef ONLINE_JUDGE
// #include "template.cpp"
// #else
// #define debug(...)
// #define debugArr(...)
// #endif

////////////////////////

// ll dist[52][52][2502];
ld arr[202020];
ld psum[202020];

int main(){
#ifdef _DEBUG   
    freopen ("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif      
    ios::sync_with_stdio(false);
    cin.tie(NULL);
    
    int N,K;cin>>N>>K;
    for(int i=1;i<=N;i++)cin>>arr[i];
    ld lo=0.0;
    ld hi=1000.0;
    int it=0;
    while(it++<=100){
        ld mid=(lo+hi)/2;
        vector<ld> p;
        ld s=0;
        for(int i=1;i<=N;i++){
            // if(i==1)p.push_back(arr[1]-mid);
            // else p.push_back(p.back()+(arr[i]-mid));
            s+=arr[i];
            p.push_back(s-i*mid);
        }
        vector<ld> lis;
        for(auto v:p){
            if(v<0)continue;
            if(lis.empty()||lis.back()<=v)lis.push_back(v);
            else *lower_bound(lis.begin(),lis.end(),v)=v;
        }
        // cout<<mid<<" "<<lis.size()<<endl;
        if(lis.size()>=K+1)lo=mid;
        else hi=mid;
    }
    cout<<fixed;
    cout<<setprecision(12);
    cout<<lo<<endl;
        
    return 0;
}