#include<bits/stdc++.h>

using namespace std;

#define int long long 
#define pb push_back
#define F first 
#define S second

const int mol=1e9+7;

int a[200005];
int bit[200005];
    int n, k;

void upd(int now, int val){
    while(now<=n){
        bit[now]=max(bit[now], val), now+=now&-now;
    }
}

int va1l(int now){
    int ans=-1;
    while(now) ans=max(ans, bit[now]), now-=now&-now;
    return ans;
}

int pre[200005];
const double eps=1e-9;
bool ok(double val){
    vector<double>ch;
    for(int i=1;i<=n;i++) ch.pb(-val*i+pre[i]);
    sort(ch.begin(), ch.end());
    int ans;
    for(int i=1;i<=n;i++) bit[i]=-1;
    for(int i=1;i<=n;i++){
        int q=0;
        if(pre[i]>=val*i||abs(pre[i]-val*i)<=eps) q=1;
        int id=lower_bound(ch.begin(), ch.end(), -val*i+pre[i])-ch.begin()+1;
        q=max(q, va1l(id)+1);
        upd(id, q);
        if(i==n) ans=q;
    }
    return ans>=k;
}
void solve(){
    cin>>n>>k;
    
    for(int i=1;i<=n;i++) cin>>a[i], pre[i]=pre[i-1]+a[i];

    double l=1, r=1000;

    for(int i=1;i<=50;i++){
        double mid=(l+r)/2;
        if(ok(mid)) l=mid;
        else r=mid;
    }
    cout<<fixed<<setprecision(10)<<l<<"\n";
}

signed main(){
    ios::sync_with_stdio(0);cin.tie(0);
    // int t;
    // cin>>t;
    // while(t--)
    solve();
    return 0;
}