#include <cstdio>
#include <vector>
#define nmax 100001
using namespace std;

typedef vector <int> A[nmax];
A a1,a2,v;
typedef bool VIZ[nmax];
VIZ viz,viz1,viz2;

unsigned int n,m,x,y,i,j,nr;

void citire()
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    scanf("%d%d",&n,&m);
    for(i=1;i<=m;i++)
    {
        scanf("%d%d",&x,&y);
        a1[x].push_back(y);
        a2[y].push_back(x);
    }
}

void dfs(int i, A a, VIZ Viz)
{
    Viz[i]=1;
    for(unsigned int j=0;j<a[i].size();j++)
        if(!Viz[a[i][j]]) dfs(a[i][j],a,Viz);
}

int main()
{
    citire();
    for(i=1;i<=n;i++)
    {
        if (!viz[i])
        {
            dfs(i,a1,viz1);
            dfs(i,a2,viz2);
            nr++;
            for(j=1;j<=n;j++)
            {
                if (viz1[j]&&viz2[j])
                    viz[j]=1, v[nr].push_back(j);
                viz1[j]=0;
                viz2[j]=0;
            }
        }
    }
    printf("%d\n",nr);
    for(i=1;i<=nr;i++)
    {
        for(j=0;j<v[i].size();j++)
            printf("%d ",v[i][j]);
        printf("\n");
    }
    return 0;
}