#include <bits/stdc++.h>

using namespace std;
vector<int>edges[200005];
vector<int>components[100005];
vector<int>mirror[200005];
int lista[100005];
bool seen[100005];
int viewed[100005];
int cnt=0, counter=0;
void dfs(int a)
{
    seen[a]=1;
    for (auto it:edges[a])
    {
        if (!seen[it])
            dfs(it);
    }
    lista[++counter]=a;
}
void dfs2(int a)
{
    viewed[a]=cnt;
    for (auto it:mirror[a])
    {
        if (viewed[it]==0)
            dfs2(it);
    }
}
int main()
{
    ifstream cin ("ctc.in");
    ofstream cout ("ctc.out");
    int n, m, a, b;
    cin>>n>>m;
    for (int i=1; i<=m; i++)
    {
        cin>>a>>b;
        edges[a].push_back(b);
    }
    for (int i=1; i<=n; i++)
        if (!seen[i])
            dfs(i);
    ///inservam muchiile
    for (int i=1; i<=n; i++)
    {
        for (int j=0; j<edges[i].size(); j++)
        {
            mirror[edges[i][j]].push_back(i);
        }
    }
    for (int i=n; i>=1; i--)
    {
        if (!viewed[lista[i]])
            {
                cnt++;
                dfs2(lista[i]);
            }
            ///cout<<viewed[lista[i]]<<" ";
    }
    ///cout<<'\n';
    for (int i=1; i<=n; i++)
    {
        components[viewed[i]].push_back(i);
    }
    cout<<cnt<<'\n';
    for (int i=1; i<=cnt; i++)
    {
        for (int j=0; j<components[i].size(); j++)
        {
            cout<<components[i][j]<<" ";
        }
        cout<<'\n';
    }
}