#include <bits/stdc++.h>
using namespace std;
int i,comp[100005],viz[100005],nr,n,m,x,y,vect[100005],l;
vector <int> v[100005];
vector <int> vt[100005];
vector <int> ras[100005];
void dfs(int nod)
{
    int i;
    viz[nod]=1;
    nr++;
    vect[nr]=nod;
    for(i=0;i<v[nod].size();i++)
        if(viz[v[nod][i]]==0)dfs(v[nod][i]);
}
void dfp(int nod)
{
    int i;
    comp[nod]=nr;
    viz[nod]=1;
    for(i=0;i<vt[nod].size();i++)
        if(viz[vt[nod][i]]==0)dfp(vt[nod][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);
        vt[y].push_back(x);
    }
    for(i=1;i<=n;i++)
        if(viz[i]==0)dfs(i);
    for(i=1;i<=n;i++)
        viz[i]=0;
    nr=0;
    for(i=n;i>=1;i--)
    {
        if(viz[i]==0)
        {
            nr++;
            dfp(vect[i]);
        }
    }
    printf("%d\n",nr);
    for(i=1;i<=n;i++)
        ras[comp[i]].push_back(i);
    for(l=1;l<=nr;l++)
    {
        for(i=0;i<ras[l].size();i++)
            printf("%d ",ras[l][i]);
        printf("\n");
    }
    return 0;
}