C++ :

#include <algorithm>
#include <iostream>
#include <cstdlib>
#include <cstdio>
#include <cmath>
using namespace std;
const int inf=1e9+10;
const int maxn=5e2+10;
const int maxm=1e5+10;
namespace Dinic
{
	struct edge{int to,cap,flow,last;}line[maxm];
	int n,s,t,pos=1,head[maxn],que[maxn],dis[maxn],vis[maxn],cur[maxn];
	
	void Init(int _n,int _s,int _t){n=_n; s=_s; t=_t;}
	void AddEdge(int from,int to,int cap)
	{
		line[++pos]=(edge){to,cap,0,head[from]}; head[from]=pos;
		line[++pos]=(edge){from,0,0,head[to]}; head[to]=pos;
	}
	bool BFS()
	{
		for(int i=1;i<=n;++i)vis[i]=false;
		int lead=0,tail=1; que[tail]=s; vis[s]=true; 
		while(lead<tail)
		{
			int u=que[++lead];
			for(int i=head[u];i;i=line[i].last)
			{
				edge e=line[i];
				if(!vis[e.to] && e.cap>e.flow)
				{
					vis[e.to]=true;
					que[++tail]=e.to;
					dis[e.to]=dis[u]+1;
				}
			}
		}
		return vis[t];
	}
	int DFS(int u,int a)
	{
		if(u==t || a==0)return a;
		int flow=0,f;
		for(int &i=cur[u];i;i=line[i].last)
		{
			edge &e=line[i];
			if(dis[e.to]==dis[u]+1 && (f=DFS(e.to,min(a,e.cap-e.flow)))>0)
			{
				e.flow+=f; line[i^1].flow-=f;
				flow+=f; a-=f; if(a==0)break;
			}
		}
		return flow;
	}
	int Maxflow()
	{
		int flow=0;
		while(BFS())
		{
			for(int i=1;i<=n;++i)cur[i]=head[i];
			flow+=DFS(s,inf);
		}
		return flow;
	}
	void Solve(int m,int *fa,int *son)
	{
		for(int u=1;u<=m;++u)
			for(int i=head[u];i;i=line[i].last)
				if(line[i].flow==1)fa[line[i].to-m]=u,son[u]=line[i].to-m;
	}
}
int n,m,s,t,fa[maxn],son[maxn];
void init()
{
	scanf("%d%d",&n,&m); s=n+n+1; t=n+n+2; int a,b;
	for(int i=1;i<=n;++i)Dinic :: AddEdge(s,i,1);
	for(int i=1;i<=n;++i)Dinic :: AddEdge(i+n,t,1);
	for(int i=1;i<=m;++i)
	{
		scanf("%d%d",&a,&b);
		Dinic :: AddEdge(a,b+n,1);
	}
	Dinic :: Init(n+n+2,s,t);
}
void solve()
{
	int ans=n-Dinic :: Maxflow();
	Dinic :: Solve(n,fa,son);
	for(int i=1;i<=n;++i)if(!fa[i])
	{
		int t=i;
		while(t)printf("%d ",t),t=son[t];
		printf("\n");
	}
	printf("%d\n",ans);
}
int main()
{
	init();
	solve();
	return 0;
}