#include <fstream>
#include <vector>

using namespace std;

FILE *f=freopen("ctc.in","r",stdin);
FILE *g=freopen("ctc.out","w",stdout);

vector <int> G[100001],GT[100001];
int viz[100001],k;
int n,m;
void read();
void solve();
void DFS(int);
void DFST(int);
void write();
int main(){
    read();
    solve();
    write();
    return 0;
}

void read(){
    int x,y;
    scanf("%d%d",&n,&m);
    for (int i=1;i<=m;i++){
        scanf("%d%d",&x,&y);
        G[x].push_back(y);
        GT[y].push_back(x);
    }
}

void solve(){
    for (int i=1;i<=n;i++){
        if (!viz[i]){
            DFS(i);
        }
    }
    k=1;
    for (int i=1;i<=n;i++){
        if (viz[i]==1){
            k++;
            DFST(i);
        }
    }
}

void DFS(int x){
    viz[x]=1;
    for (int i=0;i<G[x].size();i++){
        if (!viz[G[x][i]]){
            DFS(G[x][i]);
        }
    }
}

void DFST(int x){
    viz[x]=k;
    for (int i=0;i<GT[x].size();i++){
        if (viz[GT[x][i]]==1){
            DFST(GT[x][i]);
        }
    }
}

void write(){
    printf("%d\n",k-1);
    for (int i=2;i<=k;i++){
        for (int j=1;j<=n;j++){
            if (viz[j]==i){
                printf("%d ",j);
            }
        }
        printf("\n");
    }
}