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

int x,y,n,m,i,comp;
bool fr[100002];
vector<int> g[100002],ginv[100002],da[100002],S;
void dfs(int start)
{
    fr[start]=1;
    for(auto x:g[start])
        if(fr[x]==0)
            dfs(x);
    S.push_back(start);
}
void dfsinv(int start)
{
    da[comp].push_back(start);
    fr[start]=1;
    for(auto x:ginv[start])
        if(fr[x]==0)
            dfsinv(x);
}


int main()
{
    fin>>n>>m;
    for(i=1;i<=m;i++)
    {
        fin>>x>>y;
        g[x].push_back(y);
        ginv[y].push_back(x);
    }
    for(i=1;i<=n;i++)
        if(fr[i]==0)
            dfs(i);
    for(i=1;i<=n;i++)
        fr[i]=0;
    for(vector<int>::reverse_iterator it = S.rbegin() ; it != S.rend() ; it ++)
        if(!fr[*it]) {
                comp ++;
                dfsinv(*it);
        }
    fout<<comp<<'\n';
    for(i=1;i<=comp;i++)
    {
        for(auto j:da[i])
            fout<<j<<' ';
        fout<<'\n';
    }
    return 0;
}