#include <fstream>
#include <vector>
#include <stack>
using namespace std;

const int nmax = 100005;
vector <int> g[nmax], ctc[nmax];
stack <int> st;
int low[nmax], lev[nmax], nr;
bool viz[nmax];

void tarjan(int dad)
{
    int i, son, nod;
    low[dad]=lev[dad];
    viz[dad]=true;
    st.push(dad);
    for(i=0; i<g[dad].size(); i++)
    {
        son=g[dad][i];
        if(lev[son]==0)
        {
            lev[son]=lev[dad]+1;
            tarjan(son);
            low[dad]=min(low[dad], low[son]);
        }
        else if(viz[son]==true)
            low[dad]=min(low[dad], low[son]);
    }
    if(low[dad]==lev[dad])
    {
        nr++;
        do{
            nod=st.top();
            st.pop();
            ctc[nr].push_back(nod);
            viz[nod]=false;
        }while(nod!=dad);
    }
}

int main()
{
    ifstream fin ("ctc.in");
    ofstream fout ("ctc.out");
    ios_base::sync_with_stdio(false);
    int n, m, x, y, i, j;
    fin >> n >> m;
    for(i=1; i<=m; i++)
    {
        fin >> x >> y;
        g[x].push_back(y);
    }
    for(i=1; i<=n; i++)
        if(lev[i]==0)
        {
            lev[i]=1;
            tarjan(i);
        }

    fout << nr << "\n";
    for(i=1; i<=nr; i++)
    {
        for(j=0; j<ctc[i].size(); j++)
            fout << ctc[i][j] << " ";
        fout << "\n";
    }
    return 0;
}