#include <fstream>
#include <cstring>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#define pu(x) ((x^(x-1))&x)

using namespace std;

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

vector <int> v[100010],ans[100010],vt[100010];
int n,m,i,j,nr,postordine[100010],nrc;
bool use[100010];

void topsort(int x)
{
    use[x]=1;
    for (int i=0; i<v[x].size(); i++)
        if (!use[v[x][i]])
            topsort(v[x][i]);
    postordine[++nr]=x;
}

void dfs(int x)
{
    use[x]=0;
    ans[nrc].push_back(x);
    for (int i=0; i<vt[x].size(); i++)
        if (use[vt[x][i]])
            dfs(vt[x][i]);
}

int main()
{
    fin >> n >> m;
    for (i=1; i<=m; i++)
    {
        int x,y;
        fin >> x >> y;
        v[x].push_back(y);
        vt[y].push_back(x);
    }
    for (i=1; i<=n; i++)
        if (!use[i])
            topsort(i);
    for (i=nr; i; i--)
        if (use[postordine[i]])
        {
            nrc++;
            dfs(postordine[i]);
        }
    fout << nrc << '\n';
    for (i=1; i<=nrc; i++)
    {
        for (j=0; j<ans[i].size(); j++)
            fout << ans[i][j] << ' ';
        fout << '\n';
    }
}