#include <fstream>
#include <iostream>
#include <stack>
#include <vector>
#define DIM 100001
#define INF 2000000000
using namespace std;
ifstream fi("ctc.in");
ofstream fo("ctc.out");
int n,m,nr;
vector<int> V[DIM];
int MIN[DIM];
int VIZ[DIM];
stack<int> S;
int ES[DIM];
vector<int> REZ[DIM];
int rez;
void dfs(int v)
{
    VIZ[v]=MIN[v]=++nr;
    S.push(v);
    ES[v]=1;
    for(int i=0;i<V[v].size();i++)
    {
        if(!VIZ[V[v][i]])
            dfs(V[v][i]);
        if(ES[V[v][i]])
            MIN[v]=min(MIN[v],MIN[V[v][i]]);
    }
    if(VIZ[v]==MIN[v])
    {
        rez++;
        while(!S.empty() && S.top()!=v)
        {
            REZ[rez].push_back(S.top());
            ES[S.top()]=0;
            S.pop();
        }
        REZ[rez].push_back(S.top());
        ES[S.top()]=0;
        S.pop();
    }
}
int main()
{
    fi>>n>>m;
    for(int i=1;i<=m;i++)
    {
        int a,b;
        fi>>a>>b;
        V[a].push_back(b);
    }
    for(int i=1;i<=n;i++)
        MIN[i]=INF;
    for(int i=1;i<=n;i++)
        if(!VIZ[i])
            dfs(i);
    fo<<rez<<"\n";
    for(int i=1;i<=rez;i++)
    {
        for(int j=0;j<REZ[i].size();j++)
            fo<<REZ[i][j]<<" ";
        fo<<"\n";
    }
    fi.close();
    fo.close();
    return 0;
}