#include<cstdio>

#include<cstring>

#include<iostream>

#include<vector>

#include<algorithm>

using namespace std;

const int maxn=;

bool isins[maxn];

int low[maxn],dfn[maxn];

int zhan[maxn],top=;

vector<int>tu[maxn];

vector<int>lt[maxn];

int lts=;

int js=,n,m;

void tarjan(int i)

{

    int j;

    dfn[i]=low[i]=++js;

    isins[i]=;

    zhan[top++]=i;

    for(j=;j<tu[i].size();j++)

    {

        int tp=tu[i][j];

        if(dfn[tp]==-)

            tarjan(tp),

            low[i]=min(low[i],low[tp]);

        else if(isins[tp])

            low[i]=min(low[i],dfn[tp]);

    }

    if(dfn[i]==low[i])

    {

        lts++;

        do{

            j=zhan[--top];

            isins[j]=;

            lt[lts].push_back(j);

        }while(i!=j);

    }

}

void solve(int n)

{

    memset(dfn,-,sizeof dfn);

    memset(low,-,sizeof low);

    memset(zhan,-,sizeof zhan);

    memset(isins,,sizeof isins);

    for(int i=;i<n;i++)

      if(dfn[i]==-)

        tarjan(i);

}

int main()

{

    cin>>n>>m;

    for(int i=;i<=m;i++)

    {

        int a,b;

        cin>>a>>b;

        tu[a].push_back(b);

    }

    solve(n);

    for(int i=;i<=lts;i++)

    {

        cout<<i<<":";

        for(int j=;j<lt[i].size();j++)

            cout<<lt[i][j]<<" ";

        cout<<endl;

    }

    return ;

}