#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 10;
const int mod = 1e9 + 7;
const int INF = 0x3f3f3f3f;
const long long LLINF = 0x3f3f3f3f3f3f3f3fLL;
struct Node{
	int l, r;
}e[N];
int dep[N];
bool wq[N], wm[N];//完全二叉树，完美二叉树
void dfs(int u){
	if(u == 0) return;
	int l = e[u].l, r = e[u].r;
	if(l) dfs(l);
	if(r) dfs(r);
	dep[u] = max(dep[l], dep[r]) + 1;
	if(wm[l] && wm[r] && dep[l] == dep[r]){
		wm[u] = 1;
		wq[u] = 1;
	}
	else if(wq[l] && wm[r] && dep[l] == dep[r] + 1){
		wq[u] = 1;
	}
	else if(wm[l] && wq[r] && dep[l] == dep[r]){
		wq[u] = 1;
	}
}
int main(){
	int n;
	cin >> n;
	for(int i = 1 ; i <= n ; i++){
		cin >> e[i].l >> e[i].r;
	}
	memset(wm, 0, sizeof(wm));
	memset(wq, 0, sizeof(wq));
	wq[0] = 1, wm[0] = 1;
	dep[0] = 0;
	dfs(1);
	int cnt = 0;
	for(int i = 1 ; i <= n ; i++){
		if(wq[i]) cnt++;
	}
	cout << cnt << endl;
	return 0;
}