#include <fstream>
#include <vector>
#include <algorithm>
using namespace std;
ifstream in("ctc.in");
ofstream out("ctc.out");
int n,m,a,b,used[100005],cntctc;
vector<int>g[100005];
vector<int>gt[100005];
vector<int>ctc[100005];
vector<int>sortop;

void dfs(int x)
{
    used[x]=1;

    for(auto e : g[x])
        if(used[e]==0)
            dfs(e);
    sortop.push_back(x);
}
void dfs2(int x)
{
    used[x]=1;
    ctc[cntctc].push_back(x);
    for(auto e:gt[x])
        if(used[e]==0)
            dfs2(e);

}
int main()
{
    in>>n>>m;
    for(int i=1;i<=m;i++)
    {
        in>>a>>b;
        g[a].push_back(b);
        gt[b].push_back(a);
    }
    for(int i=1;i<=n;i++)
        if(used[i]==0)
            dfs(i);
    reverse(sortop.begin(), sortop.end());
    for(int i=1;i<=n;i++)used[i]=0;

    for(auto e : sortop)
        if(used[e]==0){
            cntctc++;
            dfs2(e);
        }

    out<<cntctc<<'\n';
    for(int i=1;i<=cntctc;i++)
    {
        sort(ctc[i].begin(),ctc[i].end());
        for(auto e : ctc[i])
            out<<e<<' ';
        out<<'\n';
    }
    return 0;
}