#include <fstream>
#include <vector>
#define N 100005
using namespace std;

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

vector <int> muchii[N], muchiit[N], rez[N];
int n, m, viz[N], S[N], top, vizt[N], cate;

void DFS(int nod) {

    int i;
    viz[nod] = 1;
    for ( auto i: muchii[nod])
        if (viz[i] == 0)
            DFS(i);

    S[++top] = nod;
}

void DFSt(int nod) {

    int i;
    vizt[nod] = 1;

    rez[cate].push_back(nod);

    for( auto i: muchiit[nod])
        if(vizt[i] == 0) {
            DFSt(i);
        }
}

int main()
{
    int i, x, y, j;

    fin >> n >> m;

    for (i = 1; i <= m; i++) {

        fin >> x >> y;
        muchii[x].push_back(y);
        muchiit[y].push_back(x);
    }

    for ( i = 1; i <= n; i++)
        if(viz[i] == 0)
            DFS(i);

    while(top != 0) {

        if(vizt[S[top]] == 0) {
            cate++;
          //  rez[cate].push_back(S[top]);
            DFSt(S[top]);

        }
        top--;
    }

    fout << cate << "\n";

    for ( i = 1; i <= cate; i++) {

        for ( auto j: rez[i])
            fout << j << " ";

        fout << "\n";
    }

    return 0;
}