#include <iostream>
#include <vector>
#include <list>

using namespace std;


struct Node {
	Node(){
		count=0;
		finished=false;
	}
	int i;
	int parent;
	int count;
	bool finished;
};

void count(vector<Node> &nodes,Node &node,list<Node*> path)
{
	if(node.parent>=0)
	{
		Node &parent = nodes[node.parent];

		path.push_back(&node);
		count(nodes,parent,path);
		path.pop_back();
		node.finished=true;
	}

	for( Node *child: path){
		if(!child->finished && child->i > node.i){
			cout << child->i << ":" << node.i << endl;
			child->count++;
		}
	}
}

int main() {
	
	int N;
	cin >> N;
	vector<Node> nodes(N);

	nodes[0].i=0;
	nodes[0].parent=-1;

	for(int i=1;i<nodes.size();i++){
		int parent;
		cin >> parent;
		nodes[i].i = i;
		nodes[i].parent = parent;
	}

	list<Node*> path;
	for(int i=1;i<nodes.size();i++){
		Node &node = nodes[i];
		count(nodes,node,path);
	}
	int ans = 0;
	for(int i=0;i<nodes.size();i++){
		ans += nodes[i].count;
	}
	cout << ans;

	// your code goes here
	return 0;
}