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

using namespace std;

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

vector <int> G[NMAX],GTR[NMAX],sol[NMAX];
int uz[NMAX], post[NMAX];
int n, m,comp;
void citire();
void DFS(int);
void DFSTR(int);

int main()
{
    int i, j;
    citire();
    for (i=1; i<=n; ++i)
        if (uz[i]==0) // daca nu am trecut deja prin varful respectiv
            DFS(i); // facem dfs
    for(i=n; i>=1; i--)
        if(uz[post[i]]==0)
            {
                comp++;
                DFSTR(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;
            G[x].push_back(y); // punem  elementul y  in vectorul G[x]
            GTR[y].push_back(x); // punem elementul x in vectorul GTR[y]
        }
}
void DFS (int x)
{
    int i;
    uz[x]=1; // marchez vf ca fiind folosit
    for (i=0; i<G[x].size(); i++) // i merge pana la dimensiunea lui G
        if (uz[G[x][i]]==0)
            DFS(G[x][i]);
}
void DFSTR (int x)
{
    int i;
    uz[x]=1; // marchez vf ca fiind folosit
    sol[comp].push_back(x); // pe linia curenta apelez vf k
    for (i=0; i<GTR[x].size(); i++)
        if (uz[GTR[x][i]]==0)
            DFSTR(GTR[x][i]);

}