#include <fstream>
#include <vector>
#include <bitset>
#include <stack>

using namespace std;

#define NMAX 100005

vector<int> g[NMAX], t[NMAX], sol[NMAX];
bitset<NMAX> visited;
stack<int> st;
int n,m,nr=0;

void dfs(int nod)
{
    visited[nod] = 1;
    for (auto &i : g[nod])
        if (!visited[i])
            dfs(i);
    st.push(nod);
}

void dfst(int nod)
{
    visited[nod]=0;
    sol[nr].push_back(nod);
    for (auto &i : t[nod])
        if (visited[i])
            dfst(i);
}

int main()
{
    ifstream fin("ctc.in");
    fin >> n >> m;
    int x,y;
    for (int i = 0; i < m; i++)
    {
        fin >> x >> y;
        --x;--y;
        g[x].push_back(y);
        t[y].push_back(x);
    }
    
    for (int i = 0; i<n; i++)
        if (!visited[i])
            dfs(i);
    
    while (!st.empty()) {
        if (visited[st.top()])
        {
            dfst(st.top());
            ++nr;
        }
        st.pop();
    }
    
    ofstream fout("ctc.out");
    fout << nr << endl;
    for (int i = 0;i<nr; i++)
    {
        for(auto &j : sol[i])
            fout << j+1 << " ";
        fout << endl;
    }
    fout.close();
    
    return 0;
}