#include <bits/stdc++.h>

using namespace std;

int n,m,top,nrc;
int st[100003];
bool viz[100003];
vector<int>L1[100003],L2[100003],sol[100003];

void Citire()
{
    int i,x,y;
    ifstream fin("ctc.in");
    fin>>n>>m;
    for(i=1;i<=m;++i)
    {
        fin>>x>>y;
        L1[x].push_back(y);
        L2[y].push_back(x);
    }
    fin.close();
}

void DFS1(int nod)
{
    viz[nod]=true;
    for(auto i : L1[nod])
        if(!viz[i])
            DFS1(i);
    st[++top]=nod;
}

void DFS2(int nod)
{
    viz[nod]=false;
    for(auto i : L2[nod])
        if(viz[i])
            DFS2(i);
    sol[nrc].push_back(nod);
}

void Solutie()
{
    int i;
    for(i=1;i<=n;++i)
        if(!viz[i])
            DFS1(i);
    while(top)
    {
        i=st[top--];
        if(viz[i]==1)
        {
            nrc++;
            DFS2(i);
        }
    }
}

void Afisare()
{
    int i;
    unsigned int j;
    ofstream fout("ctc.out");
    fout<<nrc<<"\n";
    for(i=1;i<=nrc;++i)
    {
        for(j=0;j<sol[i].size();++j)
            fout<<sol[i][j]<<" ";
        fout<<"\n";
    }
}

int main()
{
    Citire();
    Solutie();
    Afisare();
    return 0;
}