FIREWORKS

#include <bits/stdc++.h>
#define ll long long
using namespace std;

const int N = 2e5 + 5;

int n, m;
vector<int> a[N];
int d[N], dem[N];
bool ok = false;
ll ans;

ll rood(int u) {
    if(dem[u] > 1) return u;

    if(dem[u] == 1) {
        int uv = a[u][0];
        rood(uv);
    }
}

void DFS(int u) {
    for(int v : a[u]) {
        if(v != 0) {
            d[v] = d[u] + 1;
            DFS(v);
        }
    }
}

void solve() {

    for(int i = 2; i <= n; ++i) {
        int x; cin >> x;
        a[x].push_back(i);
        dem[x]++;
        if(dem[x] >= 2) ok = true;
    }

    if(!ok) {
        cout << n * m << '\n';
        return;
    }

    if(dem[1] == n-1) {
        cout << 3*m << '\n';
        return;
    }

    int maxx = 0, minn = 0;
    ll uv = 1;
    uv = max(uv, rood(1));

    for(int i = 1; i <= n; ++i)
        a[i].push_back(0);

    for(int u : a[uv]) {
        if(a[u].size() != 1) {
            fill(d + 1, d + n + 1, 0);
            DFS(u);

            int k = *max_element(d + 1, d + n + 1);
            if(maxx < k) {
                minn = maxx;
                maxx = k;
            }
            else if(minn < k) {
                minn = k;
            }
        }
    }
    maxx += 2; minn++;
    //cout << uv << ' ' << maxx << ' ' << minn << '\n';

    ans = (maxx*m + (uv-1) * (m-1)) + (minn + (maxx+uv-1) * (m-1));
    cout << ans << '\n';
}

int main()
{
    freopen("in.txt", "r", stdin);
    //freopen("FIREWORKS.inp", "r", stdin);
    //freopen("FIREWORKS.out", "w", stdout);
    ios_base::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);

    cin >> n >> m;
    solve();

    return 0;
}