#include <bits/stdc++.h>

using namespace std;
ifstream in("biconex.in");
ofstream out("biconex.out");
int n,m,x,y,idx[100005],low[100005],vis[100005],st[100005],t,k,nrc;
vector<int> v[100005];
vector<int> comp[100005];
void dfs(int nod)
{
    vis[nod]=1;
    idx[nod]=t;
    low[nod]=t;
    st[++k]=nod;
    t++;
    for(auto it:v[nod])
        if(vis[it]==0)
        {
          dfs(it);
          if(low[it]>=low[nod])
          {
              nrc++;
              while(st[k]!=it)
              {
                  comp[nrc].push_back(st[k]);
                  k--;
              }
              comp[nrc].push_back(it);
              k--;
              comp[nrc].push_back(nod);
          }
          low[nod]=min(low[nod],low[it]);
        }
        else low[nod]=min(low[nod],idx[it]);
}
int main()
{
    in>>n>>m;
    for(int i=1;i<=m;i++)
    {
        in>>x>>y;
        v[x].push_back(y);
    }
    t=1;
    dfs(1);
    out<<nrc<<'\n';
    for(int i=1;i<=nrc;i++)
    {
        for(auto it:comp[i])
            out<<it<<" ";
        out<<'\n';
    }
    return 0;
}