#include <bits/stdc++.h>

using namespace std;

long long readInt(long long l,long long r,char endd){
    long long x=0;
    int cnt=0;
    int fi=-1;
    bool is_neg=false;
    while(true){
        char g=getchar();
        if(g=='-'){
            assert(fi==-1);
            is_neg=true;
            continue;
        }
        if('0'<=g && g<='9'){
            x*=10;
            x+=g-'0';
            if(cnt==0){
                fi=g-'0';
            }
            cnt++;
            assert(fi!=0 || cnt==1);
            assert(fi!=0 || is_neg==false);

            assert(!(cnt>19 || ( cnt==19 && fi>1) ));
        } else if(g==endd){
            assert(cnt>0);
            if(is_neg){
                x= -x;
            }
            assert(l<=x && x<=r);
            return x;
        } else {
            assert(false);
        }
    }
}
string readString(int l,int r,char endd){
    string ret="";
    int cnt=0;
    while(true){
        char g=getchar();
        assert(g!=-1);
        if(g==endd){
            break;
        }
        cnt++;
        ret+=g;
    }
    assert(l<=cnt && cnt<=r);
    return ret;
}
long long readIntSp(long long l,long long r){
    return readInt(l,r,' ');
}
long long readIntLn(long long l,long long r){
    return readInt(l,r,'\n');
}
string readStringLn(int l,int r){
    return readString(l,r,'\n');
}
string readStringSp(int l,int r){
    return readString(l,r,' ');
}

const int NMAX = 1000000 + 5;

vector <int> graph[NMAX];
int deg[NMAX];

int main() {
    int N, M;
    N = readIntSp(1, 1000000);
    M = readIntLn(1, 1000000);
    for (int i = 1; i <= M; ++i) {
        int a = readIntSp(1, N);
        int b = readIntLn(1, N);
        assert(a != b);
        graph[b].push_back(a);
        ++deg[a];
    }
    assert(getchar() == -1);

    priority_queue <pair <int, int> > q;
    for (int i = 1; i <= N; ++i) {
        if (deg[i] == 0) {
            q.push(make_pair(graph[i].size(), i));
        }
    }

    vector <vector <int> > sol;
    int cnt = 0;
    while (!q.empty()) {
        vector <int> step = {q.top().second};
        q.pop();
        cnt += 1;
        if (q.size() >= 1) {
            step.push_back(q.top().second);
            q.pop();
            cnt += 1;
        }
        sol.push_back(step);
        for (auto it: step) {
            for (auto son: graph[it]) {
                --deg[son];
                if (deg[son] == 0) {
                    q.push(make_pair(graph[son].size(), son));
                }
            }
        }
    }
    assert(cnt == N);

    cout << sol.size() << endl;
    for (const auto v: sol) {
        cout << v.size();
        for (auto it: v)
            cout << ' ' << it;
        cout << '\n';
    }
    return 0;
}