#include <cstdio>
#include <vector>
#define nm 100100
using namespace std;
FILE *f,*g;

vector <int> a[nm],b[nm];
vector <int> sol[nm];
bool bf[nm];
int v[nm];
int n,m,ans;


void dfs1(int x)
{
    int i;
    bf[x] = true;

    for (i=0;i<a[x].size();i++)
        if (!bf[a[x][i]])
            dfs1(a[x][i]);
    v[++v[0]] = x;
}

void dfs2(int x)
{
    int i;

    bf[x] = false;
    sol[ans].push_back(x);

    for (i=0;i<b[x].size();i++)
        if (bf[b[x][i]])
            dfs2(b[x][i]);
}

void solve()
{
    int i,j;


    for (i=1;i<=n;i++)
        if (!bf[i])
            dfs1(i);

    for (i=n;i>=1;i--)
        if (bf[v[i]])
        {
            ans++;
            dfs2(v[i]);
        }

    fprintf(g,"%d\n",ans);

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

void read()
{
    int i,x,y;

    f = fopen("ctc.in","r");
    g = fopen("ctc.out","w");

    fscanf(f,"%d%d",&n,&m);

    for (i=1;i<=m;i++)
    {
        fscanf(f,"%d%d",&x,&y);
        a[x].push_back(y);
        b[y].push_back(x);
    }
}

int main()
{
    read();
    solve();

}