#include<iostream>
#include<fstream>
#include<vector>
#include<bitset>
using namespace std;
const int N=100000;
vector <int>s;
vector <int>a[N+1];
vector <int>b[N+1];
vector <int>ctc[N+1];
bitset<N+1>v;
int k,nc;

void dfs(int x)
{
    v[x]=1;
    for(auto y:a[x])
    {
        if(!v[y])
            dfs(y);
    }
    s.push_back(x);
}

void dfS(int x)
{
    ctc[nc].push_back(x);
    v[x]=1;
    for(auto y:b[x])
    {
        if (!v[y])
            dfs_t(y);
    }
}

int main()
{
    ifstream fin("ctc.in");
    ofstream fout("ctc.out");
    int h;
    fin>>k>>h;
    for (int i=0;i<h;i++)
    {
        int x,y;
        fin>>x>>y;
        a[x].push_back(y);
        b[y].push_back(x);
    }
    in.close();
   s)
    for (int i=1;i<=k;i++)
    {
        if (!v[i])
            dfs(i);
    }

    v.reset();
    for (int i=(int)s.size()-1;i>=0;i--)
    {
        if (!v[s[i]])
        {
            nc++;
            dfS(s[i]);
        }
    }

    fout<<nc<<endl;
    for (int i=1;i<=nc;i++)
    {

        for(auto x:ctc[i])
        {
            fout<<x<<" ";
        }
        fout<<endl;
    }
    fout.close();
    return 0;
}