#include <bits/stdc++.h>

using namespace std;
ifstream in("ctc.in");
ofstream out("ctc.out");
int n,m,x,y,vis[100005],k,ans,st[100005];
vector<int> v[100005],vt[100005],comp[100005];
void dfs(int nod)
{
    vis[nod]=1;
    for(auto it:v[nod])
        if(vis[it]==0) dfs(it);
    st[++k]=nod;
}
void dfst(int nod)
{
    vis[nod]=1;
    for(auto it:vt[nod])
        if(vis[it]==0) dfst(it);
}
int main()
{
    in>>n>>m;
    for(int i=1;i<=m;i++)
    {
        in>>x>>y;
        v[x].push_back(y);
        vt[y].push_back(x);
    }
    for(int i=1;i<=n;i++)
        if(vis[i]==0) dfs(i);
    memset(vis,0,sizeof(vis));
    while(k>0)
    {
        ans++;
        dfst(st[k]);
        while(vis[st[k]]==1&&k>0) {
            comp[ans].push_back(st[k]);
            k--;
        }
    }
    out<<ans<<'\n';
    for(int i=1;i<=ans;i++)
    {
        for(auto it:comp[i]) out<<it<<" ";
        out<<'\n';
    }
    return 0;
}