#include <iostream>
#include <bits/stdc++.h>
#include <iostream>
using namespace std;
ifstream in ("ctc.in");
ofstream out("ctc.out");
vector<int> graf[100005];
int low[100005],id[100005];
bool onstack[100005];
vector<vector<int>> sol;
stack<int> s;
int n,m,a,b;
int idc = 0;
void dfs(int x)
{
    id[x] = low[x] = idc++;
    s.push(x);
    onstack[x] = 1;
    for(auto it:graf[x]){
        if(id[it]==-1)
            dfs(it);
        if(onstack[it])
            low[x] = min(low[x],low[it]);
    }
    if(id[x] == low[x]){
        int node;
        vector<int> aux;
        do{
            node = s.top();
            aux.push_back(node);
            low[node] = id[x];
            s.pop();
        }while(node != x);
        sol.push_back(aux);
    }
}
int main()
{
    in>>n>>m;
    for(int i=0;i<m;i++){
        in>>a>>b;
        graf[a-1].emplace_back(b-1);
    }
    for(int i=0;i<n;i++)
    {
        low[i] = 0;
        id[i] = -1;
        onstack[i] = 0;
    }
    for(int i=0;i<n;i++)
        if(id[i]==-1)
            dfs(i);
    out<<sol.size()<<'\n';
    for(auto it:sol){
        for(auto j:it)
            out<<j+1<<' ';
        out<<'\n';
    }
    return 0;
}