#include <iostream>
#include <fstream>
using namespace std;

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

const int N = 100000;
const int M = 200000;
int n, m, vf[M], urm[M], lst[N], q[N], vf2[M], urm2[M], lst2[N], nr, cnt, st[N], st2[N], nvf[N];
bool viz1[N], viz2[N];

void adauga (int a, int b){
    vf[++nr] = b;
    urm[nr] = lst[a];
    lst[a] = nr;
    vf2[++nr] = b;
    urm2[nr] = lst2[a];
    lst2[a] = nr;
}

void dfs1(int x){
    viz1[x] = true;
    for(int p = lst[x]; p != 0; p = urm[p]){
        int y = vf[p];
        if(viz1[y] == false){
            dfs1(y);
        }
    }
    st[++nr] = x;
}

void dfs2(int x){
    viz2[x] = true;
    nvf[cnt]++;
    st2[++nr] = x;
    for(int p = lst2[x]; p != 0; p = urm2[p]){
        int y = vf2[p];
        if(viz2[y] == false){
            dfs2(y);
        }
    }
}


int main()
{
    int x, y;
    in >> n >> m;
    for(int i = 0; i < m; i++){
        in >> x >> y;
        adauga(x, y);
    }
    nr = 0;
    cnt = 0;
    for(int i = n; i >= 1; i--){
        if(viz2[st[i]] == false){
            cnt++;
            dfs2(st[i]);
        }
    }
    out << cnt << endl;
    int j = 1;
    for(int i = 1; i <= cnt; i++){
        for(int k = 0; k < nvf[i]; k++)
        {
            out << st2[j++] << " ";
            }
            out << endl;
    }
    return 0;
}