#include <iostream>
#include <fstream>

using namespace std;

int n, m, x, y;
int head[100005];
int to[200005];
int nxt[200005];
int edge_cnt;

int dfn[100005];
int low[100005];
int timer;

int st[100005];
int vf;
int in_st[100005];

int ans[100005];
int ans_start[100005];
int ans_end[100005];
int nr_comp;
int ans_sz;

void adauga_muchie(int u, int v) {
    edge_cnt++;
    to[edge_cnt] = v;
    nxt[edge_cnt] = head[u];
    head[u] = edge_cnt;
}

void dfs(int nod) {
    timer++;
    dfn[nod] = timer;
    low[nod] = timer;
    
    vf++;
    st[vf] = nod;
    in_st[nod] = 1;

    for (int i = head[nod]; i != 0; i = nxt[i]) {
        int vecin = to[i];
        if (dfn[vecin] == 0) {
            dfs(vecin);
            if (low[vecin] < low[nod]) {
                low[nod] = low[vecin];
            }
        } else if (in_st[vecin] == 1) {
            if (dfn[vecin] < low[nod]) {
                low[nod] = dfn[vecin];
            }
        }
    }

    if (low[nod] == dfn[nod]) {
        nr_comp++;
        ans_start[nr_comp] = ans_sz + 1;
        
        while (st[vf] != nod) {
            int curent = st[vf];
            vf--;
            in_st[curent] = 0;
            ans_sz++;
            ans[ans_sz] = curent;
        }
        
        int curent = st[vf];
        vf--;
        in_st[curent] = 0;
        ans_sz++;
        ans[ans_sz] = curent;
        
        ans_end[nr_comp] = ans_sz;
    }
}

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

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

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

    fout << nr_comp << "\n";
    for (int i = 1; i <= nr_comp; i++) {
        for (int j = ans_start[i]; j <= ans_end[i]; j++) {
            fout << ans[j] << " ";
        }
        fout << "\n";
    }

    return 0;
}