#include<bits/stdc++.h>
//#define int long long
using namespace std;
int ans[1000010], a[1000010];
int read()
{
    int x = 0,f = 1;
	char c = getchar();
    while (c != EOF && !isdigit(c)) {if (c == '-') f = -1;c = getchar();}
    while (isdigit(c)) {x = x * 10 + c - '0';c = getchar();}
    return x * f;
}
int n, m;
int ls(int p){return p << 1;}
int rs(int p){return p << 1 | 1;}
void pushup(int p){ans[p] = max(ans[ls(p)],ans[rs(p)]);}
void update(int dx, int dy, int l, int r, int p, int k)
{
	if(dx <= l and r <= dy)
	{
		ans[p] = max(ans[p], k);
		return ;
	}
	int mid = l + r >> 1;
	if(dx <= mid)update(dx, dy, l, mid, ls(p), k);
	if(mid < dy)update(dx, dy, mid + 1, r, rs(p), k);
	pushup(p);
}
int query(int dx, int dy, int l, int r, int p)
{
	if(dx <= l and r <= dy)return ans[p];
	int mid = l + r >> 1, res = -0x3f3f3f3f;
	if(dx <= mid)res = max(res, query(dx, dy, l, mid, ls(p)));
	if(mid < dy)res = max(res, query(dx, dy, mid + 1, r, rs(p)));
	return res;
}
int dp[1000010], b[1000010];
int sum[1000010];
pair<int, int>tmp[1000010];
bool check(int x)
{
	//cout<<x<<endl;
	sum[0] = 0;
	b[0] = 0;
	for(int i=1;i<=4*n;i++)ans[i] = -1;
	for(int i = 1;i <= n;i ++)
	{
		dp[i] = -1;
		tmp[i] = make_pair(tmp[i-1].first+(a[i]-x), i);
		b[i] = b[i-1]+(a[i]-x);
		//cout<<b[i]<<' ';
	}
	//cout<<endl;
	sort(tmp+1, tmp+n+1);
	int cnt = 0, tot = -11451419;
	for(int i=1;i<=n;i++)
	{
		if(tot == tmp[i].first)sum[tmp[i].second] = cnt;
		else{
			tot = tmp[i].first;
			sum[tmp[i].second] = ++cnt;
		}
	}
	//for(int i = 1;i <= n;i ++)cout<<sum[i]<<" ";
	//cout<<endl;
	dp[0] = 0;
	for(int i = 1;i <= n;i ++)
	{
		dp[i] = query(1, sum[i], 1, n, 1);
		if(dp[i] == -1 and b[i] < 0)continue;
		if(dp[i] == -1)dp[i] = 1;
		else dp[i] += 1;
		//cout<<sum[i]<<" "<<dp[i]<<endl;
		update(sum[i], sum[i], 1, n, 1, dp[i]);
	}
	//for(int i = 1;i <= n;i ++)cout<<dp[i]<<" ";
	//cout<<endl;
	return dp[n] >= m;
}
signed main()
{
	n = read();
	m = read();
	for(int i=1;i<=n;i++)a[i]=read()*10000;
	int l = 1, r = 1e7, ans = 0;
	while(l<=r)
	{
		int mid = l+r>>1;
		if(check(mid))
		{
			ans = mid;
			l = mid+1;
		}
		else r = mid-1;
	}
	printf("%.4f", double(ans)/10000.0);
	return 0;
}
//7 3
//1 3 1 2 2 2 1