#include <cstdio>
#include <vector>
#define NMax 100000
using namespace std;

vector<int> sol[NMax+1];
vector<int> A[NMax+1];
vector<int> B[NMax+1];
char deja[NMax+1];
int stiva[NMax+1];
int res,vf;

void DFS(int x)
{
    int y;

    deja[x] = 1;
    for(int i = 0; i < A[x].size(); ++i)
    {
        y = A[x][i];
        if(!deja[y]) DFS(y);
    }
    stiva[++vf] = x;
}

void DFS2(int x)
{
    int y;

    deja[x] = 0;
    for(int i = 0; i < B[x].size(); ++i)
    {
        y = B[x][i];
        if(deja[y]) DFS2(y);
    }
    sol[res].push_back(x);
}

int main(){
    FILE* fin = fopen("ctc.in","r");
    FILE* fout = fopen("ctc.out","w");

    int i,j,x,y,N,M;

    fscanf(fin,"%d %d",&N,&M);
    for(i = 1; i <= M; ++i)
    {
        fscanf(fin,"%d %d",&x,&y);
        A[x].push_back(y);
        B[y].push_back(x);
    }

    for(i = 1; i <= N; ++i)
    if(!deja[i]) DFS(i);

    for(i = N; i >= 1; --i)
    if(deja[ stiva[i] ])
    {
        ++res;
        DFS2(stiva[i]);
    }

    fprintf(fout,"%d\n",res);
    for(i = 1; i <= res; ++i)
    {
        for(j = 0; j < sol[i].size(); ++j) fprintf(fout,"%d ",sol[i][j]);
        fprintf(fout,"\n");
    }


return 0;
}