超简单

#include<bits/stdc++.h>
using namespace std;
int l[1000005],r[1000005],n;
void init(){
	cin>>n;
	int a,b;
	for(int i=1;i<=n;++i){
		cin>>a>>b;
		l[i]=a;
		r[i]=b;
	}
}
int dfs(int x){
	if(x==0)return 0;
	else return 1+max(dfs(l[x]),dfs(r[x]));
}
int main(){
	init();
	cout<<dfs(1);
	return 0;
}

#include<bits/stdc++.h>
using namespace std;
int l[1000005],r[1000005],n;
void init(){
	cin>>n;
	int a,b;
	for(int i=1;i<=n;i++){
		cin>>a>>b;
		l[i]=a;
		r[i]=b;
	}
}
int dfs(int x){
	if(x==0)return 0;
	else return 1+max(dfs(l[x]),dfs(r[x]));
}
int main(){
	init();
	cout<<dfs(1);
	return 0;
}