#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define inf INT_MAX
#define fr(i,l,r) for (i=(l); i<=(r); i++)
#define rfr(i,l,r) for (i=(l); i>=(r); i--)
template<typename T>inline void read(T &n){
    T w=1; n=0; char ch=getchar();
    while (!isdigit(ch) && ch!=EOF){ if (ch=='-') w=-1; ch=getchar(); }
    while (isdigit(ch) && ch!=EOF){ n=(n<<3)+(n<<1)+(ch&15); ch=getchar(); }
    n*=w;
}
template<typename T>inline void write(T x){
    if (x==0){ putchar('0'); return ; }
    T tmp;
    if (x>0) tmp=x;
    else tmp=-x;
    if (x<0) putchar('-');
    char F[105];
    long long cnt=0;
    while (tmp){
        F[++cnt]=tmp%10+48;
        tmp/=10;
    }
    while (cnt) putchar(F[cnt--]);
}
#define Min(x,y) x = min(x,y)
#define Max(x,y) x = max(x,y)
//基础配置=================================================================================
const ll N = 500005, M = 500005;
ll n,m;
struct edge{
    ll x,y;
};
ll cnt = 1,head[N]; edge e[M];
void addedge(ll x,ll y){
    cnt++;
    e[cnt].x = head[x];
    e[cnt].y = y;
    head[x] = cnt;
}
bool ok[N];
ll tms,dfn[N],low[N];
bool vis[N]; ll top,q[N];
ll cs; vector<ll> c[N];
void tarjan(ll x){
    ll i, go, son = 0; bool flag = false;
    dfn[x] = low[x] = ++tms;
    vis[x] = true, q[++top] = x;
    for (i=head[x]; i; i=e[i].x){
        ll go = e[i].y;
        if (!dfn[go]){
            tarjan(go);
            Min( low[x] , low[go] );
        }
        else {
            if (vis[go]) Min( low[x] , dfn[go] );
        }
    }
    if (dfn[x]==low[x]){
        cs++; c[cs].clear();
        ll p;
        do{
            p = q[top--];
            vis[p] = false;
            c[cs].push_back(p);
        }while (p!=x);
    }
}
int main(){
//	freopen(".in","r",stdin);
//	freopen(".out","w",stdout);
    ll i,j;
    read(n); read(m);
    fr(i,1,m){
        ll x,y; read(x); read(y);
        addedge(x,y);
    }
    fr(i,0,n-1)
        if (!dfn[i]) tarjan(i);
    printf("%lld\n",cs);
    fr(i,1,cs){
        printf("%lld ",c[i].size());
        for (j=0; j<c[i].size(); j++) printf("%lld ",c[i][j]);
        putchar('\n');
    }
    return 0;
}
//g++ a.cpp -o a -Wall -Wl,--stack=512000000 -std=c++11 -O2