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

using namespace std;

const int NMAX = 100005;
int nodes, edges;
vector <int> graph[NMAX], revgraph[NMAX], currscc;
vector <vector <int> > scc;
stack <int> st;
bitset <NMAX> seen;

void dfs1(int node)
{
    seen[node] = 1;
    for (auto i : graph[node])
    {
        if (seen[i] == 1)
            continue;
        dfs1(i);
    }
    st.push(node);
}

void dfs2(int node)
{
    seen[node] = 1;
    for (auto i : revgraph[node])
    {
        if (seen[i] == 1)
            continue;
        dfs2(i);
    }
    currscc.push_back(node);
}

int main()
{
    ifstream fin("ctc.in");
    ofstream fout("ctc.out");
    fin >> nodes >> edges;
    for (int i = 1;i <= edges;++i)
    {
        int x, y;
        fin >> x >> y;
        graph[x].push_back(y);
        revgraph[y].push_back(x);
    }
    for (int i = 1;i <= nodes;++i)
        if (seen[i] == 0)
            dfs1(i);
    seen.reset();
    while (!st.empty())
    {
        while (!st.empty() && seen[st.top()] == 1)
            st.pop();
        if (st.empty())
            break;
        currscc.clear();
        dfs2(st.top());
        scc.push_back(currscc);
        st.pop();
    }
    fout << scc.size() << "\n";
    for (int i = 0;i < scc.size();++i, fout << "\n")
        for (int j = 0;j < scc[i].size();++j, fout << " ")
            fout << scc[i][j];
    fin.close();
    fout.close();
    return 0;
}