#include <iostream>
#include <fstream>
#include <vector>
#include <queue>
#define DIM 100002

using namespace std;

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

int n, m, x, y, viz[DIM], low[DIM], lvl[DIM], niv, st[DIM];

vector<vector<int> > ctc;

vector<int> graf[DIM];
vector <int> q;

void make_ctc(int nod){
    vector<int> v;
    int x;
    do{
        x = q.back();
        v.push_back(x);
        st[x] = 0;
        q.pop_back();
    }while(x != nod);
    ctc.push_back(v);
}

void dfs(int nod){
    viz[nod] = 1;
    low[nod] = lvl[nod] = ++ niv;
    st[nod] = 1;
    q.push_back(nod);
    for(int i = 0; i < graf[nod].size(); ++ i){
        int nodc = graf[nod][i];
        if(!viz[nodc])
            dfs(nodc);
        if(st[nodc])
            low[nod] = min(low[nod], low[nodc]);
    }
    
    if(low[nod] == lvl[nod])
        make_ctc(nod);
}

int main(int argc, const char * argv[]) {
    in>>n>>m;
    for(int i = 1; i <= m; ++ i){
        in>>x>>y;
        graf[x].push_back(y);
    }
    
    for(int i = 1; i <= n; ++ i)
        if(!viz[i])
            dfs(i);
    
    out<<ctc.size()<<'\n';
    for(int i = 0; i < ctc.size(); ++ i){
        for(int j = 0; j < ctc[i].size(); ++ j)
            out<<ctc[i][j]<<" ";
        out<<'\n';
    }
    
    return 0;
}