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

using namespace std;

const int nmx = 100002;

int n,m,f[2*nmx],nr,total;
vector <int> g[nmx],gn[nmx];
stack <int> st;
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);
        gn[nod2].push_back(nod1);
    }
}

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

void dfs(int nod, int &nr) {
    viz[nod] = true;
    ++ nr;
    for(vector<int>::iterator it = gn[nod].begin(); it != gn[nod].end(); ++it)
        if(not viz[*it])
            dfs(*it,nr);
    f[++f[0]] = nod;
}

void afish() {
    printf("%d\n", total);
    for(int i = f[0]; i; --i) {
        int nr = f[i];
        while(nr--)
            printf("%d ", f[--i]);
        printf("\n");
    }
}

int main() {
    freopen("ctc.in", "r", stdin);
    freopen("ctc.out", "w", stdout);
    citire();
    for(int i = 1; i <= n; ++i)
        if(not viz[i])
            topologica(i);
    viz.reset();
    while(not st.empty()) {
        int nod = st.top();
        st.pop();
        if(viz[nod])
            continue;
        ++ total;
        nr = 0;
        dfs(nod,nr);
        f[++f[0]] = nr;
    }
    afish();
    return 0;
}