#include <cstdio>
#include <vector>
#define N 100002
#include <deque>

using namespace std;
FILE *f,*g;

vector <int> graph[N],grapht[N],ctc[N];
int sol;
int elms[N];
bool viz[N];
void dfs(int nod)
{
    viz[nod]=1;
    for(int i=0;i<grapht[nod].size();++i)
        if(!viz[grapht[nod][i]])
            dfs(grapht[nod][i]);
    ctc[sol].push_back(nod);
}

void topo(int nod)
{
    viz[nod]=1;
    for(int i=0;i<graph[nod].size();++i)
        if(!viz[graph[nod][i]])
            topo(graph[nod][i]);
    elms[++elms[0]]=nod;
}
int main()
{
    f=fopen("ctc.in","r");
    g=fopen("ctc.out","w");
    int n,m;
    fscanf(f,"%d %d",&n,&m);
    int x,y;
    for(int i=1;i<=m;++i)
    {
        fscanf(f,"%d %d",&x,&y);
        graph[x].push_back(y);
        grapht[y].push_back(x);
    }
    for(int i=1;i<=n;++i)
        if(!viz[i])
            topo(i);
    for(int i=1;i<=n;++i)
        viz[i]=0;
    for(int i=elms[0];i>=1;--i)
        if(!viz[elms[i]])
            ++sol,dfs(elms[i]);
    fprintf(g,"%d\n",sol);
    for(int i=1;i<=sol;++i)
    {
        for(int j=0;j<ctc[i].size();++j)
            fprintf(g,"%d ",ctc[i][j]);
        fprintf(g,"\n");
    }

    fclose(f);
    fclose(g);
    return 0;
}