#include <bits/stdc++.h>
#define il inline
using namespace std;
const int N=1e5+5;
int n,m,dfn[N],low[N],cnt,vis[N];
int st[N],top,bel[N],idx;
vector<int> e[N],f[N];
il void adde(int x,int y){e[x].push_back(y);}
void tarjan(int x){
    int y;dfn[x]=low[x]=++cnt,vis[x]=1,st[++top]=x;
    for(int y:e[x]){
        if(!dfn[y]) tarjan(y),low[x]=min(low[x],low[y]);
        else if(vis[y]) low[x]=min(low[x],dfn[y]);
    }
    if(dfn[x]==low[x]){
        ++idx;
        do{
            y=st[top--],bel[y]=idx,f[idx].push_back(y),vis[y]=0;
        }while(y!=x);
    }
}
int x,y,z;
int main(){
    //freopen("tarjan.in","r",stdin);
    scanf("%d%d",&n,&m);
    for(int i=1;i<=m;++i){scanf("%d%d",&x,&y),++x,++y;if(x!=y) adde(x,y);}
    for(int i=1;i<=n;++i) if(!dfn[i]) tarjan(i),top=0;
    printf("%d\n",idx);
    for(int i=idx;i;--i){
        printf("%d ",f[i].size());
        for(int x:f[i]) printf("%d ",x-1);puts("");
    }
    return 0;
}