#include <bits/stdc++.h>

#define NMAX 100007
#define pb push_back
using namespace std;

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

int n,m;

vector<int> g[NMAX],gt[NMAX];
bool vis[NMAX];
stack<int> s;

void dfs1(int nod){
    vis[nod]=1;

    for(auto it:g[nod])
        if(!vis[it])
            dfs1(it);

    s.push(nod);
}

vector<vector<int> > v;
vector<int> aux;

void dfs2(int nod){
    vis[nod]=1;
    aux.pb(nod);

    for(auto it:gt[nod])
        if(!vis[it])
            dfs2(it);
}

int main(){

    fin >> n >> m;

    for(int i=1; i<=m; i++){
        int x,y;

        fin >> x >> y;

        g[x].pb(y);
        gt[y].pb(x);
    }

    for(int i=1; i<=n; i++)
        if(!vis[i])
            dfs1(i);

    memset(vis,0,sizeof(vis));

    while(s.size()){
        int x=s.top();
        s.pop();

        if(!vis[x]){
            aux.clear();
            dfs2(x);
            v.pb(aux);
        }
    }

    fout << v.size() << "\n";

    for(auto it:v){
        for(auto i:it)
            fout << i << " ";

        fout << "\n";
    }

    return 0;
}