#include <iostream>
#include <fstream>
#include <vector>

#define N 100005

using namespace std;

ifstream fin("ctc.in");
ofstream fout("ctc.out");

int n, m, postord[N], nr, c;
vector <int> a[N], b[N], sol[N];
vector <bool> viz(N);

void dfs(int x)
{
    viz[x] = 1;
    for(unsigned i=0; i<a[x].size(); i++)
        if(!viz[a[x][i]]) dfs(a[x][i]);
    postord[++nr] = x;
}

void dfst(int x)
{
    viz[x] = 0;
    sol[c].push_back(x);
    for(unsigned i=0; i<b[x].size(); i++)
        if(viz[b[x][i]]) dfst(b[x][i]);
}

int main()
{
    fin>>n>>m;
    while(m--)
    {
        int x, y;
        fin>>x>>y;
        a[x].push_back(y);
        b[y].push_back(x);
    }

    for(int i=1; i<=n; i++)
        if(!viz[i]) dfs(i);
    for(int i=n; i>0; i--)
        if(viz[postord[i]])
        {
            c++;
            dfst(postord[i]);
        }
    fout<<c<<'\n';
    for(int i=1; i<=c; i++)
    {
        for(unsigned j=0; j<sol[i].size(); j++)
            fout<<sol[i][j]<<' ';
        fout<<'\n';
    }
    return 0;
}