#include <bits/stdc++.h>
#define rpd ios_base :: sync_with_stdio(0); cin.tie(0);
#define ll long long
#define fs first
#define sc second
#define pb push_back

using namespace std;

ifstream in( "ctc.in" );
ofstream out( "ctc.out");



vector <int>G[100005];
vector <int>Gt[100005];
stack<int> s;
int viz1[100005],cnt;
int viz2[100005];
vector<int> ctc[100005];

void dfs(int nod)
{
    viz1[nod]=1;
    for(int i=0;i<G[nod].size();++i)
    {
        if(!viz1[G[nod][i]])
            dfs(G[nod][i]);
    }
    s.push(nod);
}

void dfs2(int nod)
{
    viz2[nod]=1;
    ctc[cnt].pb(nod);
    for(int i=0;i<Gt[nod].size();++i)
    {
        if(!viz2[Gt[nod][i]])
            dfs2(Gt[nod][i]);
    }

}

main()
{
    //rpd;
    int n,m;
    in>>n>>m;
    for(int i=1;i<=m;++i)
    {
        int x,y;
        in>>x>>y;
        G[x].push_back(y);
        Gt[y].push_back(x);
    }
    for(int i=1;i<=n;++i)
    {
        if(!viz1[i])
            dfs(i);
    }
    while(!s.empty())
    {
        int nod=s.top();
        s.pop();
        if(!viz2[nod])
            {
                cnt++;
                dfs2(nod);
            }
    }
    for(int i=1;i<=n;i++)sort(ctc[i].begin(),ctc[i].end());
    out<<cnt<<'\n';
    for(int i=1;i<=cnt;++i)
    {
        for(int j=0;j<ctc[i].size();++j)
            out<<ctc[i][j]<<' ';
        out<<'\n';
    }
}