#include <bits/stdc++.h>

using namespace std;
ifstream f("biconex.in");
ofstream g("biconex.out");

const int NMax = 100003;

vector<int> G[NMax],ans[NMax];
stack<int> s;
int viz[NMax],low[NMax];
int n,m,x,y,T,nr;

void dfs(int nod,int tata){
    viz[nod] = viz[tata] + 1;
    low[nod] = viz[nod];
    s.push(nod);

    for(int i = 0; i < G[nod].size(); ++i){
        if(G[nod][i] != tata){
            if(!viz[G[nod][i]]){
                dfs(G[nod][i],nod);

                low[nod] = min(low[nod],low[G[nod][i]]);

                if(low[G[nod][i]] >= viz[nod]){/// e punct de articulatie
                    nr++;
                    while(!s.empty() && s.top() != nod){
                        ans[nr].push_back(s.top());
                        s.pop();
                    }
                    ans[nr].push_back(nod);
                }
            }else
                low[nod] = min(low[nod],viz[G[nod][i]]);
        }
    }
}
int main()
{
    f >> n >> m;
    for(int i = 1; i <= m; ++i){
        f >> x >> y;
        G[x].push_back(y);
    }
    for(int i = 1; i <= n; ++i){
        if(!viz[i]){
            dfs(i,0);
        }
    }
    g << nr << '\n';
    for(int i = 1; i <= nr; ++i){
        sort(ans[i].begin(),ans[i].end());
        for(int j = 0; j < ans[i].size(); ++j){
            g << ans[i][j] << ' ';
        }
        g << '\n';
    }
    return 0;
}