#include <iostream>
#include <cstdio>
#include <vector>
#include <bitset>

using namespace std;

int n,m,x,y,niv,k;
vector <int> g[100005], sol[100005], q;
int ix[100005], llk[100005];
bitset <100005> viz;

void dfs(int nod){
    q.push_back(nod);
    viz[nod] = 1;
    ix[nod] = llk[nod] = ++niv;

    for(int i : g[nod]){
        if(!viz[i]){
            dfs(i);
            llk[nod] = min(llk[nod], llk[i]);
        }
        else
            llk[nod] = min(llk[nod], llk[i]);
    }

    if(llk[nod] == ix[nod]){
        int w;
        do{
            w = q.back();
            q.pop_back();
            sol[k].push_back(w);
        }while(w!=nod);
        ++k;
    }

}

int main()
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);

    scanf("%d%d", &n,&m);
    for(int i=0;i<m;++i){
        scanf("%d%d", &x,&y);
        g[x].push_back(y);
    }

    dfs(1);

    cout<<k<<"\n";
    for(int i=0;i<k;++i){
        for(int j : sol[i])
            cout<<j<<" ";
        cout<<"\n";
    }

    return 0;
}