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

using namespace std;

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

const int NMAX = 100000 + 1;

int n, m, ind, comp;
vector <int> graf[NMAX];
int index[NMAX], lowlink[NMAX];
bool inStack[NMAX];
stack <int> st;
vector < vector <int> > sol;

void citeste() {
    int a, b;
    f >> n >> m;
    for (int i = 1; i <= m; i++) {
        f >> a >> b;
        graf[a].push_back(b);
    }
}

void tarjan(int nod) {
    int l, fiu, top;
    index[nod] = lowlink[nod] = ++ind;
    st.push(nod);inStack[nod] = true;
    l = graf[nod].size();
    for (int i = 0; i < l; i++) {
        fiu = graf[nod][i];
        if (index[fiu] == 0) tarjan(fiu);
        if (inStack[fiu]) lowlink[nod] = min(lowlink[nod], lowlink[fiu]);
    }
    if (index[nod] <= lowlink[nod]) {
        comp++;
        vector <int> solcrt;
        do {
            top = st.top();
            inStack[top] = false;
            st.pop();
            solcrt.push_back(top);
        } while(top != nod);
        sol.push_back(solcrt);
    }
}

void scrie() {
    int l;
    g << comp << '\n';
    for (int i = 0; i < comp; i++) {
        l = sol[i].size();
        for (int j = 0; j < l; j++) g << sol[i][j] << ' ';
        g << '\n';
    }
}

int main() {
    citeste();
    for (int i = 1; i <= n; i++)
        if (!index[i]) tarjan(i);
    scrie();
    return 0;
}