#pragma GCC optimize("Ofast")
#pragma GCC target("avx,avx2,fma")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx")
#include <bits/stdc++.h>
#define rep(i,n) for(int i=1;i<=n;++i)
#define pb push_back
#define mp make_pair
#define N 310000
#define inf 1000000007
using namespace std;
int n,k;
int a[N],id[N];
long double b[N];
int f[N];
int st[N];
int lowbit(int x)
{
    return x & (-x);
}
void insert(int x,int y)
{
    //cout<<x<<endl;
    while (x<=n)
    {
        st[x]=max(st[x],y);
        x+=lowbit(x);
    }
}
int get(int x)
{
        //cout<<x<<endl;

    int ret=0;
    while (x)
    {
        ret=max(ret,st[x]);
        x-=lowbit(x);
    }
    return ret;
}
bool check(long double ave)
{
    rep(i,n)b[i]=b[i-1]+a[i]-ave;
    if (b[n]<0)return 0;
    vector<long double> save; save.clear();
    rep(i,n)save.pb(b[i]);
    //rep(i,n)cout<<b[i]<<" "; puts("");
    sort(save.begin(),save.end());
    save.resize(unique(save.begin(),save.end())-save.begin());
    rep(i,n)st[i]=0;
    rep(i,n)
    {
        int x=lower_bound(save.begin(),save.end(),b[i])-save.begin()+1;
        //cout<<x<<endl;
        int t=get(x);
        f[i]=0;
        if (t==0)if (b[i]>=0)f[i]=1;
        if (t!=0)f[i]=t+1;
        insert(x,f[i]);
    }
    //cout<<f[n]<<endl;
    return f[n]>=k;
}
int main()
{
    cin>>n>>k;
    rep(i,n)scanf("%d",&a[i]);
    long double l=0,r=1000;
    for(int ti=1;ti<=50;ti++)
    {
        long double mid=(l+r)/2;
        //cout<<mid<<endl;
        if (check(mid))l=mid; else r=mid;
    }
    printf("%.10Lf\n",l);
    //cout<<check(1.713)<<endl;
    //cout<<check(0)<<endl;
    return 0;
}

answer.code: In function ‘int main()’:
answer.code:67:18: warning: ignoring return value of ‘int scanf(const char*, ...)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   67 |     rep(i,n)scanf("%d",&a[i]);
      |             ~~~~~^~~~~~~~~~~~
In file included from /usr/include/c++/13/string:43,
                 from /usr/include/c++/13/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/13/bits/stdc++.h:52,
                 from answer.code:4:
/usr/include/c++/13/bits/allocator.h: In destructor ‘constexpr std::_Vector_base<long double, std::allocator<long double> >::_Vector_impl::~_Vector_impl()’:
/usr/include/c++/13/bits/allocator.h:184:7: error: inlining failed in call to ‘always_inline’ ‘constexpr std::allocator< <template-parameter-1-1> >::~allocator() noexcept [with _Tp = long double]’: target specific option mismatch
  184 |       ~allocator() _GLIBCXX_NOTHROW { }
      |       ^
In file included from /usr/include/c++/13/vector:66,
                 from /usr/include/c++/13/functional:64,
                 from /usr/include/x86_64-linux-gnu/c++/13/bits/stdc++.h:53:
/usr/include/c++/13/bits/stl_vector.h:133:14: note: called from here
  133 |       struct _Vector_impl
      |              ^~~~~~~~~~~~