#include <bits/stdc++.h>
#define cin ci
#define cout co
using namespace std;
ifstream cin("ctc.in");
ofstream cout("ctc.out");
int n, m, x, y, ctc;
vector<vector<int>> graf, graft, ans;
vector<int> viz, componente, ord;
void dfs(int node)
{
    viz[node] = 1;
    for(auto next:graf[node])
        if(!viz[node])
            dfs(next);

    ord.push_back(node);
}
void dfst(int node)
{
    viz[node] = 1;
    componente[node] = ctc;
    for(auto next:graft[node])
        if(!viz[next])
            dfst(next);
}
int main()
{
    cin >> n >> m;
    graf.assign(n+1, vector<int>());
    graft.assign(n+1, vector<int>());
    viz.resize(n+1);
    componente.resize(n+1);
    for(int i=1; i<=m; i++)
    {
        cin >> x >> y;
        graf[x].push_back(y);
        graft[y].push_back(x);
    }
    for(int i=1; i<=n; i++)
        if(!viz[i])
            dfs(i);
    viz.assign(n+1, 0);
    for(int i=1; i<=n; i++)
        if(!viz[i])
        {
            ctc++;
            dfst(i);
        }
    ans.assign(ctc+1, vector<int>());
    for(int i=1; i<=n; i++)
        ans[componente[i]].push_back(i);
    cout << ctc << '\n';

    for(int i=1; i<=ctc; i++, cout << '\n')
        for(int j=0; j<ans[i].size(); j++)
            cout << ans[i][j] << " ";
    return 0;
}