#include <bits/stdc++.h>
using namespace std;
int n,e;
struct egh{
	int from,to,next;
}a[100010];
int k;
int pre[1000010];
void add(int u,int v){
	a[++k]={u,v,pre[u]};
	pre[u]=k;
}
struct Node{
	int x,y;
}p[100010];
bool cmp(Node s1,Node s2){
	return s1.x<s2.x||(s1.x==s2.x&&s1.y>s2.y);
}
int main(){
	cin>>n>>e;
	for (int i=1;i<=e;i++)cin>>p[i].x>>p[i].y;
	sort(p+1,p+1+e,cmp);
	for (int i=1;i<=e;i++)add(p[i].x,p[i].y);
	for (int i=1;i<=n;i++){
		if (pre[i]==0)continue;
		cout<<i<<endl;
		for (int j=pre[i];j!=0;j=a[j].next)cout<<a[j].to<<" ";
		cout<<endl;
	}
	return 0;
}