#include "../../include/aoc.hpp"
#include <bits/stdc++.h>
using namespace std;

typedef vector<string> vs;

unordered_map<string, unordered_set<string>> m;
vector<vs> found;

void rec(vs yes, vs maybe, vs no) {
	if (maybe.empty() && no.empty()) {
		found.push_back(yes);
		return;
	}

	while (!maybe.empty()) {
		string s = maybe.back();
		vs tyes = yes;
		tyes.push_back(s);
		vs tmaybe;
		for (string ss : maybe) {
			if (m[s].contains(ss)) {
				tmaybe.push_back(ss);
			}
		}
		vs tno;
		for (string ss : no) {
			if (m[s].contains(ss)) {
				tno.push_back(ss);
			}
		}
		rec(tyes, tmaybe, tno);
		maybe.pop_back();
		no.push_back(s);
	}
}

int main() {
	ios::sync_with_stdio(0);
	cin.tie(0);

	unordered_set<string> all;

	string line;
	while (getline(cin, line)) {
		string a = line.substr(0, 2);
		string b = line.substr(3, 5);
		all.insert(a);
		all.insert(b);
		m[a].insert(b);
		m[b].insert(a);
	}

	vs vm;
	vm.assign(all.begin(), all.end());
	rec({}, vm, {});

	vs *ms = nullptr;
	for (auto &c : found) {
		if (ms == nullptr || ms->size() < c.size()) {
			ms = &c;
		}
	}
	vs &msr = *ms;

	sort(msr.begin(), msr.end());
	cout << msr[0];
	for (int i = 1; i < msr.size(); i++) {
		cout << ',' << msr[i];
	}
	cout << '\n';
}