#include<bits/stdc++.h>
using namespace std;
const int maxn = 100010;
vector<int> G[maxn], G1[maxn];
stack<int> t; 
bool vis[maxn]; 
int sum;
int scc[maxn];
int n,m,u,v;
void dfs1(int u)
{
    vis[u]=1;
    for(int i=0;i<G[u].size();i++)
	{
    	v=G[u][i];
        if(!vis[v]) dfs1(v);
    }
    t.push(u);
}
void dfs2(int u, int cnt)
{ 
    vis[u]=1;
    scc[u]=sum;
    for (int i=0;i<G1[u].size();i++)
	{
        int v=G1[u][i];
        if(!vis[v])
			dfs2(v,sum);
    }
}
int main()
{
    cin>>n>>m; 
    for (int i=1;i<=m;i++)
	{
        cin>>u>>v;
        G[u].push_back(v);
        G1[v].push_back(u);
    }
    for(int i=1;i<=n;i++)
        if(!vis[i]) 
			dfs1(i);
    memset(vis,0,sizeof(vis)); 
    while(!t.empty())
	{ 
        u=t.top();
		t.pop();
        if(!vis[u])
		dfs2(u,++sum);
    }
    cout<<sum<<"\n";
    for(int i=1;i<=n;i++)
	{ 	
		for(int j=1;j<=n;j++)
		if(scc[j]==i)
			cout<<j<<" ";	
 	    cout<<"\n";	
    }
    return 0;
}
/*for(int i=1;i<=n;i++)
		if (vis[color[i]]) {
			for(int j=0;j<col[color[i]].size();j++) cout<<col[color[i]][j]<<" ";
			cout<<endl;
			vis[color[i]]=false;
		}*/