#include <bits/stdc++.h> //Andrei Alexandru a.k.a Sho10
#define ll long long
#define double long double
#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast")
#define all(a) (a).begin(), (a).end()
#define sz size
#define f first
#define s second
#define pb push_back
#define er erase
#define in insert
#define mp make_pair
#define pi pair
#define rc(s) return cout<<s,0
#define endl '\n'
#define mod 1000000007
#define PI 3.14159265359
#define MAXN 100005
#define INF 1000000005
#define LINF 1000000000000000005ll
#define CODE_START  ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
using namespace std;
ll n,m,s1=0;
vector<ll>g[100005],gr[100005];
bitset<100005>viz;
vector<ll>v,res[100005];
void dfs(ll node){
viz[node]=1;
for(auto it : g[node]){
    if(viz[it]==0){
        dfs(it);
    }
}
v.pb(node);
}
void dfs2(ll node){
viz[node]=1;
res[s1].pb(node);
for(auto it : gr[node]){
if(viz[it]==0){
    dfs2(it);
}
}
}
int32_t main(){
CODE_START;
ifstream cin("ctc.in");
ofstream cout("ctc.out");
cin>>n>>m;
for(ll i=1;i<=m;i++)
{
    ll x,y;
    cin>>x>>y;
    g[x].pb(y);
    gr[y].pb(x);
}
for(ll i=1;i<=n;i++)
{
    if(!viz[i]){
            dfs(i);
    }
}
viz.reset();
reverse(v.begin(),v.end());
for(auto it : v){
    if(!viz[it]){
            ++s1;
    dfs2(it);
    }
}
cout<<s1<<endl;
for(ll i=1;i<=s1;i++)
{
    for(auto it : res[i]){
        cout<<it<<' ';
    }
    cout<<endl;
}
}