#include <bits/stdc++.h>
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
int n,m,i,j,x,y,componenta,nr,stk[1<<17];
bool viz[1<<17];
vector <int> V[1<<17],G[1<<17],S[1<<17];
inline void sort_top(int nod)
{
    viz[nod]=1;
    for(int i=0;i<V[nod].size();++i)
        if(!viz[V[nod][i]])
            sort_top(V[nod][i]);
    stk[++nr]=nod;
}
void dfs(int nod)
{
    viz[nod]=0;
    S[componenta].push_back(nod);
    for(int i=0;i<G[nod].size();++i)
        if(viz[G[nod][i]])
            dfs(G[nod][i]);
}
int main()
{
    f>>n>>m;
    while(m--)
    {
        f>>x>>y;
        V[x].push_back(y);
        G[y].push_back(x);
    }
    for(i=1;i<=n;++i)
        if(!viz[i]) sort_top(i);
    while(nr--)
        if(viz[stk[nr+1]])
        {
            ++componenta;
            dfs(stk[nr+1]);
        }
    g<<componenta<<'\n';
    for(i=1;i<=componenta;++i,g<<'\n')
        for(j=0;j<S[i].size();++j) g<<S[i][j]<<' ';
    return 0;
}