#include <fstream>
#include <stack>
#include <vector>
#define NMAX 100005
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
vector<int>G[NMAX],Gtr[NMAX],viz,now;
stack<int>st;
vector<vector<int> >rez;
void dfs(int u)
{
    int j,v;
    viz[u]=1;
    for(j=0;j<G[u].size();++j)
    {
        v=G[u][j];
        if(viz[v]==0)
            dfs(v);
    }
    st.push(u);
}
void dfs_tr(int u)
{
    int j,v;
    viz[u]=1;
    now.push_back(u);
    for(j=0;j<Gtr[u].size();++j)
    {
        v=Gtr[u][j];
        if(viz[v]==0)
            dfs_tr(v);
    }
}
int main()
{
    int n,m,i,j,x,y;
    fin>>n>>m;
    for(i=1;i<=m;++i)
    {
        fin>>x>>y;
        G[x].push_back(y);
        Gtr[y].push_back(x);
    }
    viz.assign(n+1,0);
    for(i=1;i<=n;++i)
        if(viz[i]==0)
            dfs(i);
    viz.clear();
    viz.assign(n+1,0);
    while(!st.empty())
    {
        now.clear();
        if(viz[st.top()]==0)
        {
            dfs_tr(st.top());
            rez.push_back(now);
        }
        st.pop();
    }
    fout<<rez.size()<<"\n";
    for(i=0;i<rez.size();++i)
    {
        for(j=0;j<rez[i].size();++j)
            fout<<rez[i][j]<<" ";
        fout<<"\n";
    }
    return 0;
}