#include <bits/stdc++.h>

using namespace std;

ifstream f("ctc.in");
ofstream g("ctc.out");


const int nmax=100005;

vector<int>G[nmax];
stack<int>Q;
int n,m,x,y,tmp,ans;
int low[nmax],dt[nmax];
bool viz[nmax],smb[nmax];
vector<vector<int>>sol;

void DFS(int node)
{
    viz[node]=1;
    low[node]=dt[node]=tmp++;
    Q.push(node);
    smb[node]=1;

    for(auto x:G[node])
    {
        if(!viz[x])
        {

            DFS(x);

            low[node]=min(low[node],low[x]);
        }
        else if(smb[x])
        {
            low[node]=min(low[node],low[x]);
        }
    }

    if(low[node]==dt[node])
    {
        ans++;
        vector<int>a;
        while(!Q.empty() && Q.top()!=node)
        {
            a.push_back(Q.top());
            smb[Q.top()]=0;
            Q.pop();

            //cout<<w<<" ";
        }
            a.push_back(Q.top());
            smb[Q.top()]=0;
            Q.pop();
            //cout<<w<<"\n";
        sol.push_back(a);

    }
}

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);
    }

    g<<ans<<"\n";
    for(int i=0;i<ans;i++)
    {
        for(auto bt:sol[i])
         g<<bt<<" ";
        g<<"\n";
    }
    return 0;
}