#include <cstdio>
#include <vector>
#include <cstring>
#define MAXN 100000
using namespace std;
vector <int> graf[MAXN],trans[MAXN],comp[MAXN];
bool viz[MAXN];
int st[MAXN],vf,co;
void dfs(int nod)
{
    viz[nod]=true;
    for(unsigned int i=0;i<graf[nod].size();i++)
        if(!viz[graf[nod][i]])
            dfs(graf[nod][i]);
    st[vf++]=nod;
}
void dfstrans(int nod)
{
    viz[nod]=true;
    comp[co].push_back(nod+1);
    for(unsigned int i=0;i<trans[nod].size();i++)
        if(!viz[trans[nod][i]])
            dfstrans(trans[nod][i]);
}
int main()
{
    FILE *fin,*fout;
    fin=fopen("ctc.in","r");
    fout=fopen("ctc.out","w");
    int n,m,x,y;
    fscanf(fin,"%d%d",&n,&m);
    for(int i=0;i<m;i++)
    {
        fscanf(fin,"%d%d",&x,&y);
        x--;y--;
        graf[x].push_back(y);
        trans[y].push_back(x);
    }
    for(int i=0;i<n;i++)
        if(!viz[i])
            dfs(i);
    memset(viz,false,sizeof(viz));
    while(vf)
    {
        x=st[--vf];
        if(!viz[x])
            dfstrans(x),co++;
    }
    fprintf(fout,"%d\n",co);
    for(int i=0;i<co;i++)
    {
        for(unsigned int j=0;j<comp[i].size();j++)
            fprintf(fout,"%d ",comp[i][j]);
        fputc('\n',fout);
    }
    fclose(fin);
    fclose(fout);
    return 0;
}