#include <bits/stdc++.h>
using namespace std;
 
vector<vector<int> > graph(10,vector<int >());
map<int,int> m;
 
int bfs(int k)
{
	queue<pair<int,int> > q;
	q.push({k,0});
	int maxP = INT_MIN;
	while(q.size() != 0){
		int val = q.front().first;
		int pos = q.front().second;	
		maxP = max(maxP,pos);
	//	cout<<val<<" ";
		q.pop();
		for(int i = 0; i < graph[val].size() ; i++){
			q.push({graph[val][i],pos+1});
		}
	}
	return maxP;
}
int main() {
 
	graph[0].push_back(3);
	graph[0].push_back(2);
	graph[3].push_back(4);
	graph[4].push_back(5);
 
	cout<<bfs(0)<<endl;
 
	return 0;
}

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