#include <bits/stdc++.h>

using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");

vector<int> muchie[100005],c[100005],transpus[100005];
queue<int> coada;
int n, m, dist, a[100005], nr_comp;
bool vizitat[100005];

void dfs(int x)
{
    vizitat[x]=1;

    for(unsigned int i=0; i<muchie[x].size(); i++)
        if (!vizitat[muchie[x][i]])
            DFS(muchie[x][i]);

    dist++;
    a[dist]=x;
}



void bfs(int x)
{
    coada.push(x);
    vizitat[x]=1;

    c[nr_comp].push_back(x);

    while(!coada.empty())
    {
        x=coada.front();
        coada.pop();

        for(int i=0; i<transpus[x].size(); i++)
            if (!vizitat[transpus[x][i]])
            {
                coada.push(transpus[x][i]);
                c[nr_comp].push_back(transpus[x][i]);
                vizitat[transpus[x][i]]=1;
            }
    }
}


int main()
{

    fin>>n>>m;
    for(unsigned int i=1; i<=m; i++)
    {
        int x, y;
        fin>>x>>y;
        muchie[x].push_back(y);
        transpus[y].push_back(x);
    }

    for(unsigned int i=1; i<=n; i++)
        if (!vizitat[i])
            dfs(i);

    memset(vizitat,0,sizeof(vizitat));


    for(unsigned int i=dist; i>=1; i--)
        if (!vizitat[a[i]])
        {
            nr_comp++;
            bfs(a[i]);
        }


    fout<<nr_comp<<endl;
    for(int i=1; i<=nr_comp; i++)
    {
        for(int j=0; j<c[i].size(); j++)
            fout<<c[i][j]<<" ";
        fout<<endl;
    }

    return 0;
}