#include <bits/stdc++.h>

using namespace std;

typedef long long ll;


vector<vector<int>> a;
vector<bool> flag;
int c = 0;
int st = 0;

void dfs(int v, int mx){
    flag[v] = true;
    for(int u : a[v]){
        if(!flag[u])
            dfs(u, mx + 1);
    }
    if(mx > c){
        st = v;
        c = mx;
    }
}

int main()
{
    ll n, m;
    cin >> n >> m;
    flag.resize(n);
    a.resize(n);
    for(int i = 0; i < n - 1; ++i){
        int x;
        cin >> x;
        a[i - 1].push_back(x - 1);
        a[x - 1].push_back(i - 1);
    }
    dfs(0, 0);
    int ans = c;
    c = 0;
    flag.resize(n);
    dfs(st, 0);
    ll res = ans * (m - 1) * 2 + c;
    cout << res << endl;

}