#include <bits/stdc++.h>

using namespace std;

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

int n,m,nrc;
vector<int>h[100003];
vector<int>t[100003];
vector<int>sol[100003];
stack<int>st;
bitset<100003>viz;

void Citire()
{
    int i,x,y;
    fin>>n>>m;
    for(i=1;i<=m;i++)
    {
        fin>>x>>y;
        h[x].push_back(y);
        t[y].push_back(x);
    }
}

void DFS1(int nod)
{
    viz[nod] = 1;
    for(auto i : h[nod])
        if(viz[i] == 0)
            DFS1(i);
    st.push(nod);
}

void DFS2(int nod)
{
    viz[nod] = 1;
    sol[nrc].push_back(nod);
    for(auto i : t[nod])
        if(viz[i] == 0)
            DFS2(i);
}

void CTC()
{
    int i,k;
    for(i=1;i<=n;i++)
        if(viz[i] == 0)
            DFS1(i);

    viz.reset();
    while(!st.empty())
        if(viz[i] == 0)
        {
            k = st.top();
            st.pop();
            if(viz[k] == 0)
            {
                nrc++;
                DFS2(k);
            }
        }
}

void Afisare()
{
    int i;
    fout<<nrc<<"\n";
    for(i=1;i<=nrc;i++)
    {
        for(auto j : sol[i])
            fout<<j<<" ";
        fout<<"\n";
    }
}

int main()
{
    Citire();
    CTC();
    Afisare();

    fin.close();
    fout.close();
    return 0;
}