//#include <iostream>
#include <vector>
#include <algorithm>
#include <cstring>

using namespace std;
ifstream cin("ctc.in");
ofstream cout("ctc.out");
vector <int> v[100005],rev[100005],co[100005];
int viz[100005],order[100005],comp,cont;
void dfs(int nod){
    viz[nod]=1;
    for(auto u:v[nod]){
        if(viz[u]==0){
            dfs(u);
        }
    }
    order[++cont]=nod;
}
void dfs_r(int nod){
    viz[nod]=1;
    co[comp].push_back(nod);
    for(auto u:rev[nod]){
        if(viz[u]==0){
           dfs_r(u);
        }
    }
}
int main()
{
    int n,m,a,b;
    cin>>n>>m;
    for(int i=1;i<=m;i++){
        cin>>a>>b;
        v[a].push_back(b);
        rev[b].push_back(a);
    }
    for(int i=1;i<=n;i++){
        if(viz[i]==0){
            dfs(i);
        }
    }
    for(int i=1;i<=n;i++){
        viz[i]=0;
    }
    for(int i=n;i>=1;i--){
        if(viz[order[i]]==0){
            comp++;
            dfs_r(order[i]);
        }
    }
    cout<<comp<<"\n";
    for(int i=1;i<=comp;i++){
        for(auto u:co[i]){
            cout<<u<<" ";
        }
        cout<<"\n";
    }
    return 0;
}