#include <fstream>
#include <vector>
#include <stack>

using namespace std;

ifstream fin("ctc.in");
ofstream fout("ctc.out");

vector<int> v[100001], vt[100001];
stack<int> s;
vector<int> viz;
vector<int> nrctc[100001];
int n, m, cnt;

void DFS(int x){
    viz[x] = 1;
    for(auto &y:v[x])
        if(!viz[y])
            DFS(y);
    s.push(x);
}

void DFST(int x){
    viz[x] = 1;
    nrctc[cnt].push_back(x);
    for(auto &y:vt[x])
        if(!viz[y])
            DFST(y);

}

int main()
{
    fin>>n>>m;
    viz.resize(n+1);
    while(m--){
        int x,y;
        fin>>x>>y;
        v[x].push_back(y);
        vt[y].push_back(x);
    }
    for(int i=1; i<=n; ++i)
        if(!viz[i])
            DFS(i);

    viz.assign(n+1, 0);
    while(!s.empty()){
        int i = s.top();
        s.pop();
        if(!viz[i]){
            cnt++;
            DFST(i);
        }
    }
    fout<<cnt<<endl;
    for(int i=1; i<=cnt; ++i){
        for(auto &e:nrctc[i])
            fout<<e<<" ";
        fout<<endl;
    }

    return 0;
}