#include <fstream>
#include <vector>
#define NM 100001
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
int nr,i,j,x,y,n,m,k,viz[NM],st[NM];
vector <int> G[NM],G2[NM],sol[NM];
void dfs(int nod){
    viz[nod]=1;
    for(int i=0;i<G[nod].size();i++)
        if(viz[G[nod][i]]==0)
            dfs(G[nod][i]);
    st[++k]=nod;
    }
void dfs2(int nod){
    sol[nr].push_back(nod);
    viz[nod]=0;
    for(int i=0;i<G2[nod].size();i++)
        if(viz[G2[nod][i]]==1)
            dfs2(G2[nod][i]);
                      }

int main()
{
f>>n>>m;
for(i=1;i<=m;i++){
    f>>x>>y;
    G[x].push_back(y);
    G2[y].push_back(x);
}
for(i=1;i<=n;i++)
    if(viz[i]==0)
        dfs(i);
while(k>0){
    nr++;
         dfs2(st[k]);
    while(k>0&&viz[st[k]]==0)
        k--;
}
g<<nr<<'\n';
for(i=1;i<=nr;i++){
    for(j=0;j<sol[i].size();j++)
        g<<sol[i][j]<<" ";
    g<<'\n';
}


    return 0;
}