#include<bits/stdc++.h>
using namespace std;
int main()
{
	int n,l,r,a[1000001],amx=1;
	scanf("%d",&n);
	a[1]=1;
	for(int i=1;i<=n;i++)
	{
		cin>>l>>r;
		if(amx<a[i])
		{
			amx=a[i];
		}
		a[r]=a[i]+1;
		a[l]=a[i]+1;
	}
	cout<<amx;
	return 0;
}

本地：Process exited after 1.775 seconds with return value 3221225725

emmmmm

蒟蒻求调