#include <bits/stdc++.h>

using namespace std;
ifstream fin ("ctc.in");
ofstream fout("ctc.out");
vector <int> v[200005];
vector <int> v2[200005];
vector <vector <int> > ans;
vector <int> H;
int uz[200005];
int n,m,x,y,i,j,k;
void citire()
{
    fin>>n>>m;
    for(i=1; i<=m; i++)
       {
        fin>>x>>y;
    v[x].push_back(y);
    v2[y].push_back(x);
       }

}
void dfs(int nod)
{
    uz[nod]=1;
    for(auto it : v[nod])
    {
        if(uz[it]) continue;
        dfs(it);
    }
    H.push_back(nod);
}
void dfs2(int nod)
{
    uz[nod]=1;
    for(auto it : v2[nod])
    {
        if(uz[it]) continue;
        dfs2(it);
    }
    ans.back().push_back(nod);
}
int main()
{
    citire();
    for(int i=1; i<=n; i++)
        if(!uz[i])
        dfs(i);
    memset(uz,0,sizeof(uz));
    for(int i=H.size()-1; i>=0; i--)
        if(!uz[H[i]])
        {
            ans.push_back(vector<int>());
            dfs2(H[i]);
            k++;
        }

    fout<<k<<endl;
    for(auto i: ans)

    {
       sort(i.begin(),i.end());
        for(auto j: i)
            fout<<j<<" ";


        fout<<endl;
    }
    return 0;
}