#include<cstdio>
#include<vector>

using namespace std;

vector<int> v[100010];
vector<int> vt[100010];
vector<int> comp[100010];
int a[100010],sz;
bool viz[100010];
int n,m,x,y,nr;

void build(int nod)
{
    viz[nod]=1;
    int next;
    while(!v[nod].empty())
    {
        next=v[nod].back();
        v[nod].pop_back();
        if(viz[next]==0)
        {
            build(next);
        }
    }
    sz++;
    a[sz]=nod;
}

void fillcomp(int nod)
{
    comp[nr].push_back(nod);
    viz[nod]=1;
    int next;
    while(!vt[nod].empty())
    {
        next=vt[nod].back();
        vt[nod].pop_back();
        if(viz[next]==0)
        {
            fillcomp(next);
        }
    }
}

int main()
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);

    scanf("%d %d",&n,&m);
    for(int i=1;i<=m;i++)
    {
        scanf("%d %d",&x,&y);
        v[x].push_back(y);
        vt[y].push_back(x);
    }

    for(int i=1;i<=n;i++)
    {
        if(viz[i]==0)
        {
            build(i);
        }
    }

    for(int i=1;i<=n;i++)
    {
        viz[i]=0;
    }

    for(int i=n;i>0;i--)
    {
        if(viz[a[i]]==0)
        {
            nr++;
            fillcomp(a[i]);
        }
    }
    printf("%d\n",nr);
    for(int i=1;i<=nr;i++)
    {
        while(!comp[i].empty())
        {
            printf("%d ",comp[i].back());
            comp[i].pop_back();
        }
        printf("\n");
    }
}