//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2")
//#pragma GCC optimize("Ofast","unroll-loops","inline")
#include<bits/stdc++.h>
#define ll long long
//#define int ll
#define pb push_back
#define pii pair<int,int>
#define MP make_pair
#define fi first
#define se second
using namespace std;
const int N=2e5+10,M=1e6+10,mod=998244353;
const double eps=1e-5;
int n,k,a[N],w[N],tot,f[N];
double b[N],c[N];
struct Bit{
	int s[N];
	inline void init(){memset(s,0,sizeof(s));}
	inline int lb(int x){return x&(-x);}
	void upd(int x,int v){for(;x<=n;x+=lb(x)) s[x]=max(s[x],v);}
	int qry(int x){int res=0;for(;x;x-=lb(x)) res=max(res,s[x]);return res;}
}tr;
bool chk(double x){
	tot=0;
	tr.init();
	for(int i=1;i<=n;i++) b[i]=a[i]-x;
	for(int i=1;i<=n;i++) b[i]+=b[i-1],c[++tot]=b[i];
	sort(c+1,c+tot+1);tot=unique(c+1,c+tot+1)-c-1;
	for(int i=1;i<=n;i++){
		if(b[i]>=0) w[i]=lower_bound(c+1,c+tot+1,b[i])-c;
		else w[i]=-1;
	}
	for(int i=1;i<=n;i++) f[i]=0;
	for(int i=1;i<=n;i++) if(w[i]!=-1) f[i]=tr.qry(w[i])+1,tr.upd(w[i],f[i]);
	return f[n]>=k;
}
signed main(){
//	freopen("a.in","r",stdin);
//	freopen("a.out","w",stdout);
	scanf("%d%d",&n,&k);
	for(int i=1;i<=n;i++) scanf("%d",&a[i]);
	double l=1,r=3;
	while(r-l>eps){
		double mid=(l+r)/2;
		if(chk(mid)) l=mid;
		else r=mid;
	}
	printf("%.8lf\n",(l+r)/2);
	return 0;
}