import java.util.*;
import java.io.*;

public class Graph
{
    int V;
    LinkedList<Integer> list[];

    Graph(int V){
        this.V=V;
        list=new LinkedList[V];
        for(int i=0;i<V;i++){
            list[i]=new LinkedList<Integer>();
        }
    }

    public void addedge(int x,int y)
    {
        list[x].addFirst(y);
    }

    public void printgraph(){
        for (int i = 0; i <V ; i++) {
            LinkedList<Integer> nlist = list[i];
            if(nlist.isEmpty()==false) {
                System.out.print("source = " + i + " => ");
                for (int j = 0; j < nlist.size(); j++) {
                    System.out.print(" " + nlist.get(j));
                }
            }
            System.out.println();
        }
    }


    public void DFSrec(){
        boolean visited[] = new boolean [V];

        for(int i=0;i<V;i++)
        {
            if(!visited[i]){
             dfs(i,visited);
            }
        }
    }

    public void dfs(int v, boolean visited[])
    {
        visited[v] = true;
        System.out.print(v+" ");
        for(int i=0;i<list[v].size();i++)
        {
            int V = list[v].get(i);
            if(!visited[V])
                dfs(V,visited);
        }
    }

    public static void main(String [] args){
        Graph g = new Graph(7);
        g.addedge(1,3);
        g.addedge(2,3);
        g.addedge(0,4);
        g.addedge(4,5);
        g.addedge(5,6);
        g.printgraph();
        g.DFSrec();
    }
}
/* solution  */

/*
Finished in 60 ms
source = 0 =>  4
source = 1 =>  3
source = 2 =>  3

source = 4 =>  5
source = 5 =>  6

0 4 5 6 1 3 2

*/