#include <bits/stdc++.h>
#include <fstream>
using namespace std;

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

int n, m;
int nmax = 100000;
vector<int> L[100001], LT[100001], nodes;
vector<int> viz(nmax + 1, 0);
vector<vector<int>> Ctc;
stack<int> q;

void dfs1(int node)
{
    viz[node] = 1;

    for(auto v: L[node])
    {
        if(viz[v] == 0)
            dfs1(v);
    }

    q.push(node);
}

void dfs2(int node)
{
    viz[node] = 1;
    nodes.push_back(node);

    for(auto v: LT[node])
    {
        if(viz[v] == 0)
            dfs2(v);
    }
}

int main()
{
    fin >> n >> m;
    int ctc = 0;

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

        L[x].push_back(y);
        LT[y].push_back(x);
    }

    for(int i = 1; i <= n; i ++)
    {
        if(viz[i] == 0) dfs1(i);
    }

    for(int i = 1; i <= n; i ++)
        viz[i] = 0;

    while(!q.empty())
    {
        int node = q.top();
        q.pop();

        if(viz[node]) continue;

        nodes.clear();
        ctc++;
        dfs2(node);
        Ctc.push_back(nodes);
    }

    fout << ctc << '\n';

    for(auto v: Ctc)
    {
        for(auto n: v)
            fout << n << ' ';
        fout << '\n';
    }

    return 0;
}