#include <bits/stdc++.h>
#define MAX  2000

using namespace std;

vector<int> topSort(int node, vector<int> &indeg, vector<vector<int> > &adj)
{
    vector<int> ans;
    for(int i=0; i<node; i++) //Inserting all independent nodes first
    {
        if(indeg[i]==0) ans.push_back(i);
    }

    for(int i=0; i<ans.size(); i++)
    {
        int u=ans[i];
        for(int j=0; j<adj[u].size(); j++)
        {
            int v=adj[u][j];
            indeg[v]--;
            if(indeg[v]==0) ans.push_back(v);
        }
    }
    if(ans.size()!=node) ans.clear(); //cycle found, so returning empty vector
    return ans;
}

int main()
{
    //freopen("in.txt","r",stdin);
    //freopen("out.txt","w",stdout);

    int node, edge;
    cout<<"Enter the number of nodes and edges: ";

    while(cin>>node>>edge) //assuming node>=0, edges>=0
    {
        vector<int> indeg(node,0);
        vector<vector<int> > adj(node);
        /* //for string input
        unordered_map<string,int> mp;
        unordered_map<int,string> mp;
        int c=0;
        */

        if(edge==0) //Print all nodes as all are independent
        {
            for(int i=0; i<node; i++) cout<<i<<" ";
            cout<<endl;
        }

        cout<<"Enter the relations(pair of edges): "<<endl;

        for(int i=0; i<edge; i++) //Populating Adjacency list and indeg array for TopSort
        {
            int from,to;
            //string from,to;
            cin>>from>>to;

            /* //Processing string input

            if(mp1[from]==0)
            {
                mp1[from]=++c;
                mp2[c]=from;
            }
            if(mp1[to]==0)
            {
                mp1[to]=++c;
                mp2[c]=to;
            }
            g[mp1[from]].pb(mp1[to]);
            indeg[mp1[to]]++;
            */
            adj[from].push_back(to);
            indeg[to]++;
        }

        vector<int> ans=topSort(node, indeg, adj);

        if(ans.size()>0) //Ordering possible
        {
            cout<<"The correct ordering is:";
            for(int i=0; i<ans.size(); i++)
            {
                cout<<" "<<ans[i];
                //cout<<mp2[ans[i]]<<" ";
            }
            cout<<endl;
        }
        else cout<<"Cycle exists"<<endl; //Ordering not possible
    }
    return 0;
}