#include <bits/stdc++.h>
#define inf 1000000001

using namespace std;

ifstream f("ctc.in");
ofstream g("ctc.out");

vector<int>v[100001],sol[100001];
int n,m,k,t,low[100001],disc[100001];
bool fol[100001];
stack<int>sk;

void dfs(int nod)
{
    t++;
    sk.push(nod);
    fol[nod]=true;
    disc[nod]=low[nod]=t;
    for(int i=0;i<v[nod].size();++i)
    {

        if(!disc[v[nod][i]])
        {

            dfs(v[nod][i]);
            low[nod]=min(low[nod],low[v[nod][i]]);

        }
        else if(fol[v[nod][i]])low[nod]=min(low[nod],disc[v[nod][i]]);

    }

    if(low[nod]==disc[nod])
    {
        k++;
        while(sk.top()!=nod)
        {
            sol[k].push_back(sk.top());
            fol[sk.top()]=false;
            sk.pop();
        }

        sol[k].push_back(sk.top());
            fol[sk.top()]=false;
            sk.pop();

    }

}

int main()
{
    f>>n>>m;
    for(int i=1;i<=m;++i)
    {
        int x,y;
        f>>x>>y;
        v[x].push_back(y);
    }

    for(int i=1;i<=n;++i)
        if(!disc[i])
        {
            t = 0;
            dfs(i);
        }

    g<<k<<'\n';

    for(int i=1;i<=k;++i)
    {
        for(auto j=0;j<sol[i].size();++j)
        {
            g<<sol[i][j]<<" ";
        }
        g<<'\n';
    }

    return 0;
}