#include <bits/stdc++.h>
#define NMAX 100000
using namespace std;

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

vector<int> e[NMAX + 5];
vector<int> te[NMAX + 5];
vector<int> st;
vector<vector<int>> scc;

int viz[NMAX + 5], tviz[NMAX + 5];

void dfs(int node)
{
    viz[node] = 1;
    for(auto adj : e[node])
        if(!viz[adj])
            dfs(adj);
    st.push_back(node);
}

void tdfs(int node)
{
    tviz[node] = 1;
    scc.back().push_back(node);
    for(auto adj : te[node])
        if(!tviz[adj])
            tdfs(adj);
}

int main()
{
    int n, m;
    fin >> n >> m;
    for(int i = 1; i<=m; i++)
    {
        int x, y;
        fin >> x >> y;
        e[x].push_back(y);
        te[y].push_back(x);
    }
    for(int i = 1; i<=n; i++)
        if(!viz[i])
            dfs(i);
    while(!st.empty())
    {
        int i = st.back();
        st.pop_back();
        if(!tviz[i])
        {
            vector<int> tmp;
            scc.push_back(tmp);
            tdfs(i);
        }
    }
    fout << scc.size() << '\n';
    for(auto vs : scc)
    {
        for(auto i : vs)
            fout << i << ' ';
        fout << '\n';
    }
    return 0;
}