#include<bits/stdc++.h>
#define int long long
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");

vector<int>v[100005],inv[100005],ans[100005];
int n,m,viz[100005],sol[100005],k,cnt;

void dfs(int nod)
{
    viz[nod]=1;
    for(auto it:v[nod])
        if(viz[it]==0)
            dfs(it);
    sol[++k]=nod;
}

void dfs_inv(int nod)
{
    viz[nod]=1;
    ans[cnt].push_back(nod);
    for(auto it:inv[nod])
        if(viz[it]==0)
            dfs_inv(it);
}

void kosaraju()
{
    int i;
    for(i=1;i<=n;i++)
        if(viz[i]==0)
            dfs(i);
    for(i=1;i<=n;i++)
        viz[i]=0;
    cnt=0;
    for(i=k;i>=1;i--)
        if(viz[sol[i]]==0)
            cnt++,dfs_inv(sol[i]);
}

signed main()
{
    int i,x,y;
    f>>n>>m;
    for(i=1;i<=m;i++)
    {
        f>>x>>y;
        v[x].push_back(y);
        inv[y].push_back(x);
    }
    kosaraju();
    g<<cnt<<'\n';
    for(i=1;i<=n;i++)
    {
        for(auto it:ans[i])
            g<<it<<" ";
        g<<'\n';
    }
    return 0;
}