#include <bits/stdc++.h>
#define cin fin
#define cout fout
using namespace std;
ifstream cin ("ctc.in");
ofstream cout ("ctc.out");
int n,m,a,b,i,viz[100008],v[100008],cnt,cnt2;
vector<int>G1[100008],G2[100008],ras[100008];
void postordine(int nod)
{
    viz[nod]=1;
    for(auto i:G1[nod])
    {
        if(viz[i]==0)
        postordine(i);
    }
    v[++cnt]=nod;
}
void dfs(int nod)
{
    viz[nod]=0;
    ras[cnt2].push_back(nod);
    for(auto i:G2[nod])
    {
        if(viz[i]==1)
        dfs(i);
    }
    v[++cnt]=nod;
}
int main()
{
    cin>>n>>m;
    for(i=1;i<=m;i++)
    {
        cin>>a>>b;
        G1[a].push_back(b);
        G2[b].push_back(a);
    }
    for(i=1;i<=n;i++)
    {
        if(viz[i]==0)
            postordine(i);
    }
    for(i=cnt;i>=1;i--)
    {
        if(viz[v[i]]==1)
        {
            cnt2++;
            dfs(v[i]);
        }
    }
    cout<<cnt2<<'\n';
    for(i=1;i<=cnt2;i++)
    {
        for(auto j:ras[i])
            cout<<j<<" ";
        cout<<'\n';
    }
    return 0;
}