#include <fstream>
#include <vector>
#define NMAX 100001

using namespace std;

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

vector <int> org[NMAX],trs[NMAX],sol[NMAX];
int uz[NMAX], post[NMAX];
int n, m, lg, comp;

void citire();
void dfs_initial(int);
void dfs_transpus(int);

int main()
{
    int i, j;
    citire();
    for (i=1; i<=n; ++i)
        if (uz[i]==0)
            dfs_initial(i);
    for(i=1; i<=n; i++)
        uz[i]=0;
    for(i=n; i>=1; i--)
        if(uz[post[i]]==0)
            {
            comp++;
            dfs_transpus(post[i]);
            }
    fout<<comp<<'\n';
    for(i=1;i<=comp;i++)
        {
        for(j=0;j<sol[i].size();j++)
            fout<<sol[i][j]<<' ';
        fout<<'\n';
        }
    return 0;
}
void citire()
{
    int x,y,i;
    fin>>n>>m;
    for(i=1; i<=m; i++)
        {
        fin>>x>>y;
        org[x].push_back(y);
        trs[y].push_back(x);
        }
}
void dfs_initial (int k)
{
    int i;
    uz[k]=1;
    for (i=0; i<org[k].size(); i++)
        if (uz[org[k][i]]==0)
            dfs_initial(org[k][i]);
    post[++lg]=k;
}
void dfs_transpus (int k)
{
    int i;
    uz[k]=1;
    sol[comp].push_back(k);
    for (i=0; i<trs[k].size(); i++)
        if (uz[trs[k][i]]==0)
            dfs_transpus(trs[k][i]);

}