#include <stdio.h>
#include <vector>
#include <stack>

#define NMAX 100005

using namespace std;

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

int n,i,j,x,y,nrcomp,nod,m;
bool viz[NMAX];

vector <int> graf[NMAX],invers[NMAX],comp[NMAX];
stack <int> st;

void dfs(int x)
{
    int i;

    viz[x] = true;

    if(!graf[x].empty())
        for(i=0; i<=graf[x].size()-1; ++i)
            if(!viz[graf[x][i]])
                dfs(graf[x][i]);

    st.push(x);
}

void dfsinv(int x)
{
    int i;

    viz[x] = true;

    if(!invers[x].empty())
        for(i=0; i<=invers[x].size()-1; ++i)
            if(!viz[invers[x][i]])
                dfsinv(invers[x][i]);

    comp[nrcomp].push_back(x);
}

int main()
{
    fscanf(fin, "%d%d", &n,&m);
    for(i=1; i<=m; ++i)
    {
        fscanf(fin, "%d%d", &x,&y);
        graf[x].push_back(y);
        invers[y].push_back(x);
    }

    for(i=1; i<=n; ++i)
        if(!graf[i].empty() and !viz[i])
            dfs(i);

    for(i=1; i<=n; ++i)
        viz[i] = false;

    while(!st.empty())
    {
        nod = st.top();
        if(!viz[nod])
        {
            ++nrcomp;
            dfsinv(nod);
        }
        st.pop();
    }

    fprintf(fout, "%d\n", nrcomp);
    for(i=1; i<=nrcomp; ++i)
    {
        for(j=0; j<=comp[i].size()-1; ++j)
            fprintf(fout, "%d ", comp[i][j]);
        fprintf(fout, "\n");
    }
    //mama are mere

    fclose(fin);
    fclose(fout);
    return 0;
}