每次删除深度根结点的儿子中深度最大的子树显然是正确的，直接贪心即可。

#include <bits/stdc++.h>
using namespace std;
int d[200012];
struct F
{
	int to[400012], ns[400012], fs[400012], m;
	void adds(int f, int t)
	{
		m++;
		to[m] = t;
		ns[m] = fs[f];
		fs[f] = m;
	}
	void add(int f, int t)
	{
		adds(f, t);
		adds(t, f);
	}
};
F w;
int f[200012];
priority_queue <long long> pq;
int main()
{
	int n;
	cin >> n;
	for (int i = 2; i <= n; i++)
	{
		cin >> f[i];
		w.add(i, f[i]);
	}
	for (int i = n; i >= 2; i--)
	{
		d[f[i]] = max(d[f[i]], d[i] + 1);
		if (f[i] == 1) pq.push(d[i] * 1000000ll + i);
	}
	pq.push(0);
	long long ans = n - 2;
	for (int _ = 1; _ <= n - 1; _++)
	{
		long long c = pq.top() % 1000000;
		pq.pop();
		int ii = w.fs[c];
		while (ii)
		{
			if (w.to[ii] != f[c]) pq.push(d[w.to[ii]] * 1000000ll + w.to[ii]);
			ii = w.ns[ii];
		}
		ans += pq.top() / 1000000;
	}
	cout << ans << endl;
	return 0;
}