#include <fstream>
#include <vector>
#include <algorithm>
using namespace std;
ifstream cin ("ctc.in");
ofstream cout ("ctc.out");
vector <int> g[100005];
vector <int> rg[100005];
int v[100005],vf;
int n,m;
int cnt;
int cntcomp;
vector<int> comp[100005];
bool u[100005];
void dfs (int k)
{
    u[k] = true;
    for (auto vf:g[k])
    {
        if (u[vf])
            continue;
        dfs(vf);
    }
    cnt++;
    v[cnt] = k;
}
void dfsr (int k)
{
    u[k] = true;
    for (auto vf:rg[k])
    {
        if (u[vf])
            continue;
        dfsr(vf);
    }
    comp[cntcomp].push_back(k);
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    cin >> n >> m;
    int i,j;
    for (i=1;i<=m;i++)
    {
        int x,y;
        cin >> x >> y;
        g[x].push_back(y);
        rg[y].push_back(x);
    }
    for (i=1;i<=n;i++)
        if(!u[i])
            dfs(i);
    for (i=1;i<=n;i++)
        u[i] = false;
    for (i=cnt;i>=1;i--)
        if (!u[v[i]])
        {
            cntcomp++;
            dfsr(v[i]);
        }
    cout << cntcomp << '\n';
    for(i=1;i<=cntcomp;i++)
    {
        sort(comp[i].begin(),comp[i].end());
        for (j=0;j<comp[i].size();j++)
            cout << comp[i][j] << ' ';
        cout << '\n';
    }
    return 0;
}