#include <fstream>
#include <vector>
#define NM 100001
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
int nr,i,j,x,y,n,m,k,viz[NM],st[NM],d[NM],low[NM],t;
vector <int> G[NM],sol[NM];
void dfs(int nod){
    t++;
    d[nod]=low[nod]=t;
    viz[nod]=1;
    st[++k]=nod;
    for(int i=0;i<G[nod].size();i++){

        if(d[G[nod][i]]==0){
            dfs(G[nod][i]);
        low[nod]=min(low[nod],low[G[nod][i]]);
    }
            else
                if(viz[G[nod][i]]==1)
                    low[nod]=min(low[nod],low[G[nod][i]]);
    }
            if(low[nod]==d[nod]){
                nr++;
                while(x!=nod&&k>0){
                        x=st[k--];
                        sol[nr].push_back(x);
                }

            }
}

int main()
{
f>>n>>m;
for(i=1;i<=m;i++){
    f>>x>>y;
    G[x].push_back(y);
}
for(i=1;i<=n;i++)
    if(d[i]==0)
        dfs(i);

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


    return 0;
}