#include <fstream>
#include <vector>
using namespace std;
ifstream fin ("ctc.in");
ofstream fout ("ctc.out");

int viz[100010],v[100010],p,i,j,nr,ok,n,m,x,k,y;

vector<int> a[100010],b[100010],c[100010];

void dfs1 (int nod) {
    viz[nod]=1;
    for(int i=0;i<a[nod].size();i++)
        if(viz[a[nod][i]]==0)
           dfs1(a[nod][i]);
    v[++k]=nod;
}

void dfs2 (int nod) {
    viz[nod]=0;
    c[p].push_back(nod);
    k--;
    for(int i=0;i<b[nod].size();i++)
        if(viz[b[nod][i]]==1)
            dfs2(b[nod][i]);
}

int main () {
    fin>>n>>m;
    for(i=1;i<=m;i++){
        fin>>x>>y;
        a[x].push_back(y);
        b[y].push_back(x);
    }
    for(i=1;i<=n;i++)
        if(viz[i]==0)
            dfs1(i);
    while(k>0){
        if(viz[v[k]]==1)
            p++,dfs2(v[k]);
    }
    fout<<p<<"\n";
    for(i=1;i<=p;i++){
        for(j=0;j<c[i].size();j++)
            fout<<c[i][j]<<" ";
        fout<<"\n";
    }
}