#include <fstream>
#include <stack>
#include <vector>
using namespace std;

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

int n, m, nrc;
vector<vector<int>> G1, G2, cc;
vector<int> c;
vector<bool> s, s1;
stack<int> stk;

void Read();
void Df(int x);
void DfT(int x);

int main()
{
    Read();
    for (int i = 1; i <= n; i++)
        if (!s[i]) Df(i);
    int x;
    while (!stk.empty())
    {
        x = stk.top(); stk.pop();
        if (!s1[x])
        {
            nrc++;
            c.clear();
            DfT(x);
            cc.push_back(c);
        }
    }
    fout << nrc << '\n';
    for (const auto & C : cc)
    {
        for (const auto & x : C)
            fout << x << ' ';
        fout << '\n';
    }
    return 0;
}

void DfT(int x)
{
    s1[x] = true;
    c.push_back(x);
    for (const auto & e : G2[x])
        if (!s1[e]) DfT(e);
}

void Df(int x)
{
    s[x] = true;
    for (const auto & e : G1[x])
        if (!s[e]) Df(e);
    stk.push(x);
}

void Read()
{
    fin >> n >> m;
    G1 = G2 = vector<vector<int>>(n + 1);
    s = s1 = vector<bool>(n + 1);
    for (int i = 1, x, y; i <= m; i++)
    {
        fin >> x >> y;
        G1[x].push_back(y);
        G2[y].push_back(x);
    }
}