#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef unsigned long long int ull;

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
ll myRand(ll B) {
    return (ull)rng() % B;
}
inline double time() {
    return static_cast<long double>(chrono::duration_cast<chrono::nanoseconds>(chrono::steady_clock::now().time_since_epoch()).count()) * 1e-9;
}

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    vector<string> v;
    for (int i = 0; i < 52; ++i) {
        string s; cin >> s;
        v.push_back(s);
        while (1) {
            bool ed = true;
            for (int j = v.size()-1; j >= 3; --j) {
                if (v[j][0] == v[j-3][0]) {
                    ed = false;
                    v.erase(v.begin()+j);
                    v.erase(v.begin()+j-1);
                    v.erase(v.begin()+j-2);
                    v.erase(v.begin()+j-3);
                    break;
                }
            }
            if (ed) {
                for (int j = v.size()-1; j >= 3; --j) {
                    if (v[j][1] == v[j-3][1]) {
                        ed = false;
                        v.erase(v.begin()+j);
                        v.erase(v.begin()+j-3);
                        break;
                    }
                }
            }
            if (ed) break;
        }
    }
    cout << v.size();
    for (int i = 0; i < v.size(); ++i) {
        cout << " " << v[i];
    }
    cout << endl;
}