#include <bits/stdc++.h>

using namespace std;
vector <int > g[100005],gb[100005];
int n,m,viz[100005],asig[100005],nrcom;
vector <int > st,sol[100005];

void citire()
{
    scanf("%d%d",&n,&m);
    for (int i=1;i<=m;++i)
    {
        int x,y;
        scanf("%d%d",&x,&y);
        g[x].push_back(y);
        gb[y].push_back(x);
    }
}
void parcurg(int nod)
{
    viz[nod]=1;
    for (vector < int > :: iterator it=g[nod].begin();it!=g[nod].end();++it)
        if (!viz[*it])
            parcurg(*it);
    st.push_back(nod);
}
void assignez(int nod)
{
    asig[nod]=1;
    sol[nrcom].push_back(nod);
    for (vector <int > :: iterator it=gb[nod].begin();it!=gb[nod].end();++it)
        if (!asig[*it])
            assignez(*it);
}
void kosaraju()
{
    for (int i=1;i<=n;++i)
        if (!viz[i])
            parcurg(i);
    while (!st.empty())
    {
        int nod=st.back();
        if (!asig[nod])
        {
            nrcom++;
            assignez(nod);
        }
        st.pop_back();
    }
    printf("%d\n",nrcom);
    for (int i=1;i<=nrcom;++i)
    {
        for (vector <int > :: iterator it=sol[i].begin();it!=sol[i].end();++it)
            printf("%d ",*it);
        printf("\n");
    }
}
int main()
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    citire();
    kosaraju();
    return 0;
}