#include <bits/stdc++.h>

using namespace std;

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

const int N = 1e5 + 5;

int n, m;

vector <int> g[N], inv[N];

int vis[N], comp[N], visrev[N];

vector <int> ord;

vector <vector <int>> ctc;

void dfs(int nod)
{
    vis[nod] = 1;
    for(auto it:g[nod])
    {
        if(!vis[it])
            dfs(it);
    }
    ord.push_back(nod);
}

int cnt;

void dfss(int nod)
{
    ctc.back().push_back(nod);
    visrev[nod] = 1;
    for(auto it:inv[nod])
    {
        if(!visrev[it])
            dfss(it);
    }
}

int main()
{
    in >> n >> m;

    for(int i = 1; i <= m; i++)
    {
        int x, y;
        in >> x >> y;
        g[x].push_back(y);
        inv[y].push_back(x);
    }
    for(int i = 1; i <= n; i++)
    {
        if(!vis[i])
            dfs(i);
    }
    reverse(ord.begin(), ord.end());
    for(auto it:ord)
    {
        if(!visrev[it])
        {
            ctc.push_back({});
            dfss(it);
        }
    }
    out << ctc.size() << '\n';
    for(int i = 0; i < ctc.size(); i++)
    {
        for(auto x:ctc[i])
            out << x << ' ';
        out << '\n';
    }
    return 0;
}