#include <bits/stdc++.h>

using namespace std;

ifstream f("ctc.in");
ofstream g("ctc.out");

stack<int>s;
vector<int>graph[100005];
int n, m, from, to, ix[100005], llk[100005];
vector<int>rez[100005];
int ind_rez=1, ind_ix=1;
bool in_stack[100005];

void tarjan(int ind)
{
    ix[ind]=llk[ind]=ind_ix++;
    s.push(ind);
    in_stack[ind]=1;
    for (auto &v:graph[ind])
    {
        if(!ix[v])
        {
            tarjan(v);
            llk[ind]=min(llk[ind],llk[v]);
        }
        else if (in_stack[v])
            llk[ind]=min(llk[ind],llk[v]);
    }
    if (llk[ind]==ix[ind])
    {
        int sus;
        while (1)
        {
            sus=s.top();
            s.pop();
            if (llk[sus]==ix[sus])
            {
                rez[ind_rez++].push_back(sus);
                break;
            }
            else
                rez[ind_rez].push_back(sus);
        }
    }
}

int main()
{
    f >> n >> m;
    for (int i=1; i<=m; ++i)
    {
        f >> from >> to;
        graph[from].push_back(to);
    }
    for (int i=1; i<=n; ++i)
    {
        if (!ix[i])
        {
            tarjan(i);
        }
    }
    g << ind_rez-1 << '\n';
    for (int i=1; i<ind_rez; ++i)
    {
        for (auto &v:rez[i])
            g << v <<' ';
        g << '\n';
    }
    return 0;
}