#include <bits/stdc++.h>
using namespace std;
vector<vector<int>>adj(100000);
vector<vector<int>>tadj(100000);
bool vis[100000];
stack<int>q;
void dfs1(int nod){
    vis[nod] = 1;
    for(auto v : adj[nod]) if(!vis[v]) dfs1(v);
    q.push(nod);
}
void dfs2(int nod, vector<int> &tmp){
    vis[nod] = 0;
    for(auto v : tadj[nod]) if(vis[v]) dfs2(v,tmp);
    tmp.push_back(nod);
    
}
int main()
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    vector<vector<int>>ans;
    int n,m;
    cin >> n >> m;
    for(int i=0;i<m;i++){
        int a,b;
        cin >> a >> b;
        a--;
        b--;
        adj[a].push_back(b);
        tadj[b].push_back(a);
    }
    for(int i =0;i<n;i++) if(!vis[i]) dfs1(i);
    
    while(q.size()){
        int nod = q.top();
        q.pop();
        if(vis[nod]) {
            vector<int>tmp;
            dfs2(nod,tmp);
            ans.push_back(tmp);
        }
    }
    cout<<ans.size()<<"\n";
    for(auto v : ans){
        for(auto e : v) cout<<e+1<<" ";
        cout<<"\n";
    }
  

    

    return 0;
}