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

using namespace std;

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

const int nmax = 1005;

int n, m, fr[nmax], fr2[nmax], k;
vector<int> v[nmax], v2[nmax], ans[nmax];
stack<int> St;

void dfs(int nod)
{
    fr[nod] = 1;
    for(auto x : v[nod])
        if(!fr[x])
            dfs(x);

    St.push(nod);
}

void dfs2(int nod)
{
    ans[k].push_back(nod);
    fr2[nod] = 1;

    for(auto x : v2[nod])
        if(!fr2[x])
            dfs2(x);
}

int main()
{
    f >> n >> m;
    for(int i = 1; i <= m; i ++)
    {
        int x, y;
        f >> x >> y;
        v[x].push_back(y);
        v2[y].push_back(x);
    }

    for(int i = 1; i <= n; i ++)
        if(!fr[i])
            dfs(i);

    while(!St.empty())
    {
        if(!fr2[St.top()])
            k ++, dfs2(St.top());

        St.pop();
    }

    g << k << '\n';
    for(int i = 1; i <= k; i ++, g << '\n')
        for(auto x : ans[i])
            g << x << " ";
    return 0;
}