#include <fstream>
#include <vector>
#include <stack>

using namespace std;

ifstream cin("ctc.in");
ofstream cout("ctc.out")

const int N=1e5+2;

int n,m,x,y,nc;
bool viz[N],viz_t[N];

vector<int>v[N],v_t[N],ans[N];
stack<int>stv;

void dfs(int nod)
{
    viz[nod]=true;
    for(size_t i=0;i<v[nod].size();i++)
    {
        int el=v[nod][i];
        if(viz[el]==0)
        {
            dfs(el);
        }
    }
    stv.push(nod);
}

void dfs_t(int nod)
{
    ans[nc].push_back(nod);
    viz_t[nod]=true;
    for(size_t i=0;i<v_t[nod].size();i++)
    {
        int el=v_t[nod][i];
        if(viz_t[el]==0)
        {
            dfs_t(el);
        }
    }
}

int main()
{
    cin>>n>>m;
    for(int i=1;i<=m;i++)
    {
        cin>>x>>y;
        v[x].push_back(y);
        v_t[y].push_back(x);
    }
    for(int i=1;i<=n;i++)
    {
        if(viz[i]==0)
        {
            dfs(i);
        }
    }
    while(!stv.empty())
    {
        int el=stv.top();
        stv.pop();
        if(viz_t[el]==0)
        {
            nc++;
            dfs_t(el);
        }
    }
    cout<<nc<<'\n';
    for(int i=1;i<=nc;i++)
    {
        for(size_t j=0;j<ans[i].size();j++)
        {
            cout<<ans[i][j]<<" ";
        }
        cout<<'\n';
    }
    return 0;
}