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

using namespace std;
ifstream fin ("ctc.in");
ofstream fout("ctc.out");
stack<int>s;
vector<vector<int> > ans;
void dfs (int node, vector<vector<int>> &v, vector<int> &vis) {
    vis[node] = 1;
    for (int j = 0; j < (int) v[node].size(); ++j) {
        int nxt = v[node][j];
        if (!vis[nxt]) {
            dfs(nxt, v, vis);
        }
    }
    s.push(node);
}
void dfs2 (int node, int cnt, vector<vector<int>> &tr, vector<int> &vis2, vector<int> &scc)
{
    vis2[node] = 1;
    scc[node] = cnt;
    ans[cnt].push_back(node);
    for (int j = 0; j < (int) tr[node].size(); ++j) {
        int nxt = tr[node][j];
        if (!vis2[nxt]) {
            dfs2(nxt, cnt, tr, vis2, scc);
        }
    }
}

int main() {
    int n, m;
    fin >> n >> m;

    vector<int> vis(n+1), vis2(n+1), scc(n+1);
    vector<vector<int>> v(n+1), tr(n+1);
    ans.resize(n+1);

    for (int i = 1; i <= m; ++i) {
        int a, b;
        fin >> a >> b;
        v[a].push_back(b);
        tr[b].push_back(a);
    }
    for (int i = 1; i <= n; ++i) {
        if (!vis[i]) {
            dfs(i, v, vis);
        }
    }

    int cnt = 0;
    while (!s.empty()) {
        int node = s.top();
        s.pop();
        if (!vis2[node]) {
            ++cnt;
            dfs2(node, cnt, tr, vis2, scc);
        }
    }
    fout << cnt << '\n';
    for(int i = 1; i <= cnt; i++)
    {
        for(int j = 0; j < ans[i].size(); j++)
        {
            fout << ans[i][j] << ' ';
        }
        fout << '\n';
    }
    /*for (int i = 1; i <= n; ++i) {
        cout << scc[i] << " ";*/

    return 0;
}
/*
#include <iostream>
#include <vector>
#include <stack>

using namespace std;
vector<vector<int> > v, v2;
vector<vector<int> > ans;
stack<int> s;
int cnt;
int viz[100001], viz2[100001];
void dfs(int nod)
{
    viz[nod] = 1;
    for(int i = 0; i<v[nod].size(); i++)
    {
        int vecin = v[nod][i];
        if(!viz[vecin])
        {
            dfs(vecin);
        }
    }
    s.push(nod);
}
void dfs2(int nod)
{//cout << nod << ' ';
    viz2[nod] = 1;
    //ans[cnt].push_back(nod);
    for(int i = 0; i<v2[nod].size(); i++)
    {
        int vecin = v[nod][i];
        if(!viz2[vecin])
        {
            dfs2(vecin);
        }
    }

}
int main()
{
    int n, m;
    cin >> n >> m;
    v.resize(n+1), v2.resize(n+1), ans.resize(n+1);
    for(int  i = 1; i<=m; i++)
    {
        int a,b;
        cin >> a >> b;
        v[a].push_back(b);
        v2[b].push_back(a);
    }
    for(int i = 1; i<=n; i++)
    {
        if(!viz[i])
        {
            dfs(i);
        }
    }
    while(!s.empty())
    {
        int x = s.top();
        s.pop();
        if(!viz2[x])
        {
            cnt++;
            dfs2(x);
        }
    }
    /*
    cout << cnt << '\n';
    for(int i = 1; i <= cnt; i++)
    {
        for(int j = 0; j < ans[i].size(); j++)
            cout << ans[i][j] << ' ';
        cout << '\n';
    }
    return 0;
}
*/