#include <bits/stdc++.h>
using namespace std;
#define MAXN 500069
vector <vector <int> > Graph(MAXN);
int Fath[MAXN];
int Size[MAXN];
double curAns[MAXN];
double Ans;
int n,p,k;

inline void scan(int &number)
{
    cin >> number;
}

double Analise (int v)
{
    double curVa = 0;
    if (Graph[v].size() == 0) curVa = 1;
    for (auto son:Graph[v])
    {
       curVa = max(curVa, min(Analise(son), double(Size[son])/double(Size[v]-1)));
    }

    curAns[v] = curVa;
    return curVa;
}

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    scan(n);
    scan(k);
    Size[0] = 1;
    Fath[0] = -1;

    for (int i=1; i!=n; ++i)
    {
        scan(p);
        p--;
        Fath[i] = p;
        Graph[p].push_back(i);
        Size[i] = 1;
    }

    int m = n;
    while (m--) Size[Fath[m]] += Size[m];

    Analise(0);

    Ans = 0;
    for (int i=0; i!=n; ++i) if (Size[i] > k) Ans = max(Ans, curAns[i]);

    cout.precision(17);
    cout << fixed << Ans;

    return 0;
}