#include<bits/stdc++.h>
#define DIM 100010
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
int n,m,i,a,b,low[DIM],niv[DIM],l,nr,d[DIM];
vector<int> v[DIM],s,sol[DIM];
void dfs(int nod)
{
    low[nod]=niv[nod]=++l;
    s.push_back(nod);d[nod]=1;
    for(auto it:v[nod])
    {
        if(niv[it]&&d[it]) low[nod]=min(low[nod],niv[it]);
        if(niv[it]==0)
        {
            dfs(it);
            low[nod]=min(low[it],low[nod]);
        }
    }
    if(low[nod]==niv[nod])
    {
        nr++;while(s.back()!=nod) sol[nr].push_back(s.back()),d[s.back()]=0,s.pop_back();
        sol[nr].push_back(s.back()),d[s.back()]=0,s.pop_back();
    }
}

int main()
{
    fin>>n>>m;
    for(i=1;i<=m;i++)
    {
        fin>>a>>b;
        v[a].push_back(b);
    }
    for(i=1;i<=n;i++) if(niv[i]==0) dfs(i);
    fout<<nr<<"\n";
    for(i=1;i<=nr;i++)
    {
        for(auto it:sol[i]) fout<<it<<" ";
        fout<<"\n";
    }
    return 0;
}