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vector < int > adj[MAX];
int visited[ MAX ], dis[ MAX + 1 ];
queue < int > q;//queue->FIFO

void BFS( int src )
{
	q.push(src);
	dis[src] = 0;
	visited[src] = true;
	printf("Level %d: %d\n", dis[src], src);
	while( !q.empty() )
	{
		int v = q.front();
		q.pop();
		int temp;
		for( int i = 0 ; i < (int)adj[v].size() ; i++ )
		{
			temp = adj[v][i];
			if( !visited[temp] )
			{
				dis[temp] = dis[v]+1;
				visited[temp] = true;
				q.push(temp);
				printf("Level %d: %d\n", dis[temp], temp);
			}
		}
	}
}

int main()
{
	int e;//e = number of edges
	cin>>e;
	for( int i = 0 ; i < e ; i++ )
	{
		int x,y;
		cin>>x>>y;
		adj[x].push_back(y);
		adj[y].push_back(x);//bidirectional!
	}

	BFS(1);// let node 1 be the src node!
}