#include<bits/stdc++.h>
#define pb push_back
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
vector<int> g[100005];
int n, m, x, y, ans, id[100005], low[100005], idx;
vector<vector<int>> sol;
stack<int> st;
bitset<100005>in_stack(false);
void dfs(int nod)
{
    id[nod]=low[nod]=++idx;
    st.push(nod);
    in_stack[nod]=true;
    for(auto &x:g[nod])
    {
        if(id[x]==0)
        {
            dfs(x);
        }
        if(in_stack[x])
        {
            low[nod]=min(low[nod], low[x]);
        }
    }
    if(id[nod]==low[nod])
    {
        vector<int> ps;
        int nd=st.top();
        while(nd!=nod)
        {
            in_stack[nd]=false;
            st.pop();
            ps.pb(nd);
            nd=st.top();
        }
        ps.pb(nod);
        in_stack[nod]=false;
        st.pop();
        sol.pb(ps);
    }
}
int main()
{
    fin>>n>>m;
    for(int i=1; i<=m; i++)
    {
        fin>>x>>y;
        g[x].pb(y);
    }
    for(int i=1; i<=n; i++)
    {
        if(id[i]==0)
        {
            dfs(i);
        }
    }
    fout<<sol.size()<<"\n";
    for(auto &v:sol)
    {
        for(auto &x:v)
        {
            fout<<x<<" ";
        }
        fout<<"\n";
    }
    return 0;
}