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

using namespace std;

const int nmx = 100002;

int n,m;
vector <int> g[nmx],srt,gn[nmx],aux;
bitset <nmx> viz;
vector <vector<int> > ras;

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

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

void afish(){
    printf("%d\n", ras.size());
    for(size_t i = 0; i < ras.size(); ++i){
        for(int j = 0; j < ras[i].size(); ++j)
            printf("%d ", ras[i][j]);
        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])
            dfs(i);
    viz.reset();
    for(vector<int>::reverse_iterator it = srt.rbegin(); it != srt.rend(); ++it)
        if(not viz[*it]) {
            aux.clear();
            dfsnapoi(*it);
            ras.push_back(aux);
        }
    afish();
    return 0;
}