#include <fstream>
#include <vector>
#include <stack>
#include <algorithm>

#define NMAX 100005
using namespace std;

ifstream fin("ctc.in");
ofstream fout("ctc.out");

vector<int> G[NMAX], GT[NMAX], rez[NMAX];
stack<int> st;

int viz[NMAX], viz2[NMAX], cnt;
void DFS(int nod)
{
    for(int i = 0; i < G[nod].size(); ++i)
        if(!viz[G[nod][i]])
        {
            viz[G[nod][i]] = 1;
            DFS(G[nod][i]);
        }
    st.push(nod);
}

void DFST(int nod)
{
    rez[cnt].push_back(nod);
    for(int i = 0; i < GT[nod].size(); ++i)
        if(!viz2[GT[nod][i]])
        {
            viz2[GT[nod][i]] = 1;
            DFST(GT[nod][i]);
        }
}

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

    for(int i = 1; i <= m; ++i)
    {
        int x, y;
        fin >> x >> y;

        G[x].push_back(y);
        GT[y].push_back(x);
    }

    for(int i = 1; i <= n; ++i)
        if(!viz[i]){
            viz[i] = 1;
            DFS(i);
        }

    while(!st.empty())
    {
        if(!viz2[st.top()])
        {
            ++cnt;
            viz2[st.top()] = 1;
            DFST(st.top());
        }
        st.pop();
    }

    fout << cnt << '\n';
    for(int i = 1; i <= cnt; ++i){
        sort(rez[i].begin(), rez[i].end());
        for(int j = 0; j < rez[i].size(); ++j)
            fout << rez[i][j] << ' ';
        fout << '\n';
    }
    return 0;
}