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

using namespace std;
int cont=0,cnt=0;
int viz[100005];
vector<int> v1[100005],v2[100005];
int order[100005];
vector<int> comp[100005];
void dfs1(int nod){
    viz[nod]=1;
    for(auto u:v1[nod]){
        if(viz[u]==0){
            dfs1(u);
        }
    }
    order[++cont]=nod;
}

void dfs2(int nod){
    viz[nod]=1;
    comp[cnt].push_back(nod);
    for(auto u:v2[nod]){
        if(viz[u]==0){
            dfs2(u);
        }
    }
}

int main()
{
    ifstream cin("ctc.in");
    ofstream cout("ctc.out");
    int n,m,a,b;
    cin>>n>>m;
    for(int i=1;i<=m;i++){
        cin>>a>>b;
        v1[a].push_back(b);
        v2[b].push_back(a);
    }
    for(int i=1;i<=n;i++){
        if(viz[i]==0){
            dfs1(i);
        }
    }
    for(int i=1;i<=n;i++){
        viz[i]=0;
    }
    for(int i=n;i>=1;i--){
        if(viz[order[i]]==0){
            cnt++;
            dfs2(order[i]);
        }
    }
    cout<<cnt<<"\n";
    for(int i=1;i<=cnt;i++){
        for(auto j:comp[i]){
            cout<<j<<" ";
        }
        cout<<"\n";
    }
	return 0;
}