#include <cstdio>
#include <vector>

using namespace std;

const int NMAX = 100005;

vector <int> v[NMAX],t[NMAX],r[NMAX];
int sol[NMAX],viz[NMAX],nrr,nrsol;

void dfs(int p){
    viz[p]=1;
    for(int i=0;i<v[p].size();++i){
        if(viz[v[p][i]]==0)
            dfs(v[p][i]);
    }
    sol[++nrsol]=p;
}

void dfs2(int p){
    viz[p]=0;
    r[nrr].push_back(p);
    for(int i=0;i<t[p].size();++i){
        if(viz[t[p][i]]==1)
            dfs2(t[p][i]);
    }
}

int main()
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    int N,M,x,y;
    scanf("%d %d",&N,&M);
    for(int i=1;i<=M;++i){
        scanf("%d %d",&x,&y);
        v[x].push_back(y);
        t[y].push_back(x);
    }

    for(int i=1;i<=N;++i)
        if(viz[i]==0)
            dfs(i);

    for(int i=N;i>0;--i){
        if(viz[sol[i]]==1){
            ++nrr;
            dfs2(sol[i]);
        }
    }

    printf("%d\n",nrr);
    for(int i=1;i<=nrr;++i){
        for(int j=0;j<r[i].size();++j)
            printf("%d ",r[i][j]);
        printf("\n");
    }

    return 0;
}