//#include <iostream>
#include <fstream>
#include <vector>
#define pi pair<int,int>
#include <stack>
using namespace std;
ifstream cin("ctc.in");
ofstream cout("ctc.out");
vector <int>g[100005];
vector <int>gt[100005];
vector<int>sol[100005];
int f[100005], n, m;
int a,b;
stack <int>s;
int nrctc;
void dfs(int nod)
{
    f[nod]=1;
    for (auto e:g[nod])
        if (!f[e])
            dfs(e);
    s.push(nod);
}
void dfs2(int nod)
{
    sol[nrctc].push_back(nod);
    f[nod]=2;
    for (auto e:gt[nod])
        if (f[e]==1)
            dfs2(e);
}
int main()
{
    cin>>n>>m;
    while (m--)
    {
        cin>>a>>b;
        g[a].push_back(b);
        gt[b].push_back(a);
    }
    for (int i=1; i<=n; i++)
        if (!f[i])
            dfs(i);
    while (s.size())
    {
        int x=s.top();
        s.pop();
        if (f[x]==1)
        {
            nrctc++;
            dfs2(x);
        }
    }
    cout<<nrctc<<'\n';
    for (int i=1; i<=nrctc; i++)
        {
            for (int j=0; j<sol[i].size(); j++)
                cout<<sol[i][j]<<' ';
            cout<<'\n';
        }
    return 0;
}