#include <cstdio>
#include <vector>

using namespace std;
vector <int> v[100005],w[100005],sol[100005];

bool vizv[100005],vizw[100005];
int k,n,m,i,x,y,l,nrcomp,componente,st[100005];

void dfsv(int x)
{
    vizv[x]=1;
    int i,l=v[x].size();
    for (i=0; i<l; i++)
        if (vizv[v[x][i]]==0)
        dfsv(v[x][i]);
    st[++k]=x;
}

void dfsw(int x)
{
    vizw[x]=1;
    sol[componente].push_back(x);
    int i,l=w[x].size();
    for (i=0; i<l; i++)
        if (vizw[w[x][i]]==0)
        dfsw(w[x][i]);
}

int main()
{
    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);
        v[x].push_back(y);
        w[y].push_back(x);
    }
    for (i=1; i<=n; i++)
        if (vizv[i]==0)
        dfsv(i);
    while (k!=0)
    {
        x=st[k]; k--;
        if (vizw[x]==0)
        {
            componente++;
            dfsw(x);
        }
    }
    printf("%d\n",componente);
    for (nrcomp=1; nrcomp<=componente; nrcomp++)
    {
        l=sol[nrcomp].size();
        for (i=0; i<l; i++)
            printf("%d ",sol[nrcomp][i]);
        printf("\n");
    }
    return 0;
}