#include <cstdio>
#include <algorithm>
#include <bitset>
#include <vector>
using namespace std;
FILE *f=fopen("ctc.in","r");
FILE *g=fopen("ctc.out","w");
bitset <100005> used;
vector <int> gr[100005],gt[100005],V,compo[100005];
int i,N,M,x,y,nr;
void dfst(int nod)
{
    for(auto it:gt[nod])
    {
        if(used[it]==0)
        {
            used[it]=1;
            dfst(it);
        }
    }
    V.push_back(nod);
}
void dfs(int nod)
{
    for(auto it:gr[nod])
    {
        if(used[it]==0)
        {
            used[it]=1;
            dfs(it);
        }
    }
    compo[nr].push_back(nod);
}
int main()
{
    fscanf(f,"%d %d",&N,&M);
    for(i=1;i<=M;i++)
    {
        fscanf(f,"%d %d",&x,&y);
        gr[x].push_back(y);
        gt[y].push_back(x);
    }
    for(i=1;i<=N;i++)
    {
        if(!used[i])
            {used[i]=1;dfst(i);}
    }
    used.reset();
    reverse(V.begin(),V.end());
    for(auto it:V)
    {
        if(!used[it])
        {
            used[it]=1;
            dfs(it);
            nr++;
        }
    }
    fprintf(g,"%d\n",nr);
    for(i=0;i<nr;i++)
    {
        for(auto it:compo[i])
            fprintf(g,"%d ",it);
        fprintf(g,"\n");
    }
    fclose(f);
    fclose(g);
    return 0;
}