#include <iostream>
#include <vector>

using namespace std;

vector<vector<int> > graph(200000);
vector <int> dist(200000, 0), used(200000, 0);

void dfs(int v, int h) {
    dist[v] = h;
    used[v] = 1;
    for (int i = 0; i < graph[v].size(); i++) {
        if (!used[graph[v][i]]) dfs(graph[v][i], h + 1);
    }
}


int max_el(vector <int> num) {
    int res = -10000000000;
    for (int i = 0; i < num.size(); i++) {
        if (num[i] > res) res = num[i];
    }
    return res;
}


int main(){
    int n, m, v, u;
    cin >> n >> m;
    graph.resize(n);
    dist.resize(n);
    used.resize(n);
    vector <int> tree(n);
    for (int i = 0; i < n - 1; i++) {
        cin >> tree[i];
        graph[tree[i] - 1].push_back(i + 1);
        graph[i + 1].push_back(tree[i] - 1);
    }
    dfs(0, 0);
    int depth = max_el(dist);
    int max_d = -100000000000000;
    for (int i = 0; i < dist.size(); i++) {
        if (dist[i] > max_d) {
            max_d = dist[i];
            v = i;
        }
    }
    for (int i = 0; i < n; i++) {
        used[i] = 0;
    }
    dfs(v, 0);
    max_d = -10000000000000;
    for (int i = 0; i < n; i++) {
        if (dist[i] > max_d) {
            max_d = dist[i];
            u = i;
        }
    }
    if (m == 1) {
        cout << max_d + 1;
    }
    else if (max_d == 1) {
        cout << 1 + m * 2;
    }
    else {
        cout << max_d + (m - 1) * 2 + depth * (m - 1) * 2 + 1;
    }
    return 0;
}