#include <cstdio>
#include <vector>
#include <bitset>

using namespace std;

const int nmx = 100002;

int n,m,t;
vector <int> g[nmx],inv[nmx],st,fin;
bitset <nmx> viz;

void citire(){
    scanf("%d %d", &n, &m);
    int nod1, nod2;
    for(int i = 1; i <= m; ++i){
        scanf("%d %d", &nod1, &nod2);
        g[nod1].push_back(nod2);
        inv[nod2].push_back(nod1);
    }
}

void dfs1(int nod){
    viz[nod] = true;
    for(vector<int>::iterator it = g[nod].begin(); it != g[nod].end(); ++it)
        if(not viz[*it])
           dfs1(*it);
    st.push_back(nod);
}

void dfs2(int nod){
    viz[nod] = true;
    fin.push_back(nod);
    for(vector<int>::iterator it = inv[nod].begin(); it != inv[nod].end(); ++it)
        if(not viz[*it])
           dfs2(*it);

}

int main(){
    freopen("ctc.in", "r", stdin);
    freopen("ctc.out", "w", stdout);

    citire();

    for(int i = 1; i <= n; ++i)
        if(not viz[i])
           dfs1(i);

    viz.reset();

    for(vector<int>::reverse_iterator it = st.rbegin(); it != st.rend(); ++it){
        if(viz[*it])
            continue;
        ++ t;
        int nr = fin.size();
        dfs2(*it);
        fin.push_back(fin.size()-nr);
    }

    printf("%d\n", t);
    for(vector<int>::reverse_iterator it = fin.rbegin(); it != fin.rend();){
        int nr = *(it++);
        while(nr--)
            printf("%d ", *(it++));
        printf("\n");
    }

    return 0;
}