I love clean code

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define MOD 998244353
#define MOD2 1000000007
#define vt vector
#define endl '\n'
#define pb push_back
#define pf push_front
#define all(x) x.begin(),x.end()
#define sz(x) (int)((x).size())
#define uset unordered_set
#define umap unordered_map
#define mset multiset
#define fi first
#define se second
#define rep(i,a,b) for(int i=a;i<b;i++)
#define rrep(i,a,b) for(int i=a;i>=b;i--)
#define each(i,a) for(auto &i:a)
struct pii {
    int x, y;
    bool operator<(const pii &a) const { return x == a.x ? y < a.y : x < a.x; }
    bool operator>(const pii &a) const { return x == a.x ? y > a.y : x > a.x; }
    bool operator==(const pii &a) const { return x == a.x && y == a.y; }
    bool operator!=(const pii &a) const { return x != a.x || y != a.y; }
    pii operator+(const pii &a) const { return {x+a.x, y+a.y}; }
    pii operator-(const pii &a) const { return {x-a.x, y-a.y}; }
    pii operator*(const int &a) const { return {x*a, y*a}; }
    pii operator/(const int &a) const { return {x/a, y/a}; }
};
struct pll {
    ll x, y;
    bool operator<(const pll &a) const { return x == a.x ? y < a.y : x < a.x; }
    bool operator>(const pll &a) const { return x == a.x ? y > a.y : x > a.x; }
    bool operator==(const pll &a) const { return x == a.x && y == a.y; }
    bool operator!=(const pll &a) const { return x != a.x || y != a.y; }
    pll operator+(const pll &a) const { return {x+a.x, y+a.y}; }
    pll operator-(const pll &a) const { return {x-a.x, y-a.y}; }
    pll operator*(const ll &a) const { return {x*a, y*a}; }
    pll operator/(const ll &a) const { return {x/a, y/a}; }
};

template<class T> bool ckmin(T& a, const T& b) {
    return b < a ? a = b, 1 : 0; }
template<class T> bool ckmax(T& a, const T& b) {
    return a < b ? a = b, 1 : 0; }

int T, N;
int a[200005];

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    map<string,set<string>> adj;
    set<string> tot;
    string s;
    while (cin >> s) {
        string u = s.substr(0,2);
        string v = s.substr(3,2);
        tot.insert(u);
        tot.insert(v);
        adj[u].insert(v);
        adj[v].insert(u);
    }
    vt<string> v;
    for (auto &i:tot) {
        v.pb(i);
    }
    cout << sz(v) << endl;
    sort(all(v));
    //find maximal clique
    rep(i,0,sz(v)) {
        rep(j,i+1,sz(v)) {
            if (adj[v[i]].find(v[j]) == adj[v[i]].end()) {
                continue;
            }
            rep(k,j+1,sz(v)) {
                if (adj[v[i]].find(v[k]) == adj[v[i]].end() || adj[v[j]].find(v[k]) == adj[v[j]].end()) {
                    continue;
                }
                rep(l,k+1,sz(v)) {
                    if (adj[v[i]].find(v[l]) == adj[v[i]].end() || adj[v[j]].find(v[l]) == adj[v[j]].end() || adj[v[k]].find(v[l]) == adj[v[k]].end()) {
                        continue;
                    }
                    rep(m,l+1,sz(v)) {
                        if (adj[v[i]].find(v[m]) == adj[v[i]].end() || adj[v[j]].find(v[m]) == adj[v[j]].end() || adj[v[k]].find(v[m]) == adj[v[k]].end() || adj[v[l]].find(v[m]) == adj[v[l]].end()) {
                            continue;
                        }
                        rep(n,m+1,sz(v)) {
                            if (adj[v[i]].find(v[n]) == adj[v[i]].end() || adj[v[j]].find(v[n]) == adj[v[j]].end() || adj[v[k]].find(v[n]) == adj[v[k]].end() || adj[v[l]].find(v[n]) == adj[v[l]].end() || adj[v[m]].find(v[n]) == adj[v[m]].end()) {
                                continue;
                            }
                            rep(o,n+1,sz(v)) {
                                if (adj[v[i]].find(v[o]) == adj[v[i]].end() || adj[v[j]].find(v[o]) == adj[v[j]].end() || adj[v[k]].find(v[o]) == adj[v[k]].end() || adj[v[l]].find(v[o]) == adj[v[l]].end() || adj[v[m]].find(v[o]) == adj[v[m]].end() || adj[v[n]].find(v[o]) == adj[v[n]].end()) {
                                    continue;
                                }
                                rep(p,o+1,sz(v)) {
                                    if (adj[v[i]].find(v[p]) == adj[v[i]].end() || adj[v[j]].find(v[p]) == adj[v[j]].end() || adj[v[k]].find(v[p]) == adj[v[k]].end() || adj[v[l]].find(v[p]) == adj[v[l]].end() || adj[v[m]].find(v[p]) == adj[v[m]].end() || adj[v[n]].find(v[p]) == adj[v[n]].end() || adj[v[o]].find(v[p]) == adj[v[o]].end()) {
                                        continue;
                                    }
                                    rep(q,p+1,sz(v)) {
                                        if (adj[v[i]].find(v[q]) == adj[v[i]].end() || adj[v[j]].find(v[q]) == adj[v[j]].end() || adj[v[k]].find(v[q]) == adj[v[k]].end() || adj[v[l]].find(v[q]) == adj[v[l]].end() || adj[v[m]].find(v[q]) == adj[v[m]].end() || adj[v[n]].find(v[q]) == adj[v[n]].end() || adj[v[o]].find(v[q]) == adj[v[o]].end() || adj[v[p]].find(v[q]) == adj[v[p]].end()) {
                                            continue;
                                        }
                                        rep(r,q+1,sz(v)) {
                                            if (adj[v[i]].find(v[r]) == adj[v[i]].end() || adj[v[j]].find(v[r]) == adj[v[j]].end() || adj[v[k]].find(v[r]) == adj[v[k]].end() || adj[v[l]].find(v[r]) == adj[v[l]].end() || adj[v[m]].find(v[r]) == adj[v[m]].end() || adj[v[n]].find(v[r]) == adj[v[n]].end() || adj[v[o]].find(v[r]) == adj[v[o]].end() || adj[v[p]].find(v[r]) == adj[v[p]].end() || adj[v[q]].find(v[r]) == adj[v[q]].end()) {
                                                continue;
                                            }
                                            rep(s,r+1,sz(v)) {
                                                if (adj[v[i]].find(v[s]) == adj[v[i]].end() || adj[v[j]].find(v[s]) == adj[v[j]].end() || adj[v[k]].find(v[s]) == adj[v[k]].end() || adj[v[l]].find(v[s]) == adj[v[l]].end() || adj[v[m]].find(v[s]) == adj[v[m]].end() || adj[v[n]].find(v[s]) == adj[v[n]].end() || adj[v[o]].find(v[s]) == adj[v[o]].end() || adj[v[p]].find(v[s]) == adj[v[p]].end() || adj[v[q]].find(v[s]) == adj[v[q]].end() || adj[v[r]].find(v[s]) == adj[v[r]].end()) {
                                                    continue;
                                                }
                                                rep(t,s+1,sz(v)) {
                                                    if (adj[v[i]].find(v[t]) == adj[v[i]].end() || adj[v[j]].find(v[t]) == adj[v[j]].end() || adj[v[k]].find(v[t]) == adj[v[k]].end() || adj[v[l]].find(v[t]) == adj[v[l]].end() || adj[v[m]].find(v[t]) == adj[v[m]].end() || adj[v[n]].find(v[t]) == adj[v[n]].end() || adj[v[o]].find(v[t]) == adj[v[o]].end() || adj[v[p]].find(v[t]) == adj[v[p]].end() || adj[v[q]].find(v[t]) == adj[v[q]].end() || adj[v[r]].find(v[t]) == adj[v[r]].end() || adj[v[s]].find(v[t]) == adj[v[s]].end()) {
                                                        continue;
                                                    }
                                                    rep(u,t+1,sz(v)) {
                                                        if (adj[v[i]].find(v[u]) == adj[v[i]].end() || adj[v[j]].find(v[u]) == adj[v[j]].end() || adj[v[k]].find(v[u]) == adj[v[k]].end() || adj[v[l]].find(v[u]) == adj[v[l]].end() || adj[v[m]].find(v[u]) == adj[v[m]].end() || adj[v[n]].find(v[u]) == adj[v[n]].end() || adj[v[o]].find(v[u]) == adj[v[o]].end() || adj[v[p]].find(v[u]) == adj[v[p]].end() || adj[v[q]].find(v[u]) == adj[v[q]].end() || adj[v[r]].find(v[u]) == adj[v[r]].end() || adj[v[s]].find(v[u]) == adj[v[s]].end() || adj[v[t]].find(v[u]) == adj[v[t]].end()) {
                                                            continue;
                                                        }
                                                        cout << v[i] << "," << v[j] << "," << v[k] << "," << v[l] << "," << v[m] << "," << v[n] << "," << v[o] << "," << v[p] << "," << v[q] << "," << v[r] << "," << v[s] << "," << v[t] << "," << v[u] << endl;
                                                    }
                                                }
                                            }
                                        }
                                    }
                                }
                            }
                        }
                    }
                }
            }
        }
    }
    return 0;
}