#define USE_ORDERED_STATISTICS
#define BIG_BIGINT

#include <bits/stdc++.h>

#ifdef USE_ORDERED_STATISTICS
    #include <ext/pb_ds/assoc_container.hpp>
    #include <ext/pb_ds/tree_policy.hpp>
    using namespace __gnu_pbds;
#endif

using namespace std;

typedef long long int ll;
#ifdef BIG_BIGINT
    typedef __int128_t bigint;
#else
    typedef ll bigint;
#endif
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<vi> vvi;
typedef vector<vl> vvl;
typedef vector<pi> vpi;
typedef vector<pl> vpl;
typedef vector<vpi> vvpi;
typedef vector<vpl> vvpl;
typedef set<int> si;
typedef multiset<int> msi;
typedef set<ll> sl;
typedef multiset<ll> msl;
typedef long double ld;
template<class T> using func = function<T>;

#ifdef USE_ORDERED_STATISTICS
    typedef tree<
    pl,
    null_type,
    less<pl>,
    rb_tree_tag,
    tree_order_statistics_node_update>
    ordered_set;
#endif

#define clrcin cin.ignore(numeric_limits<streamsize>::max(),'\n');
#define GOGOGO ios::sync_with_stdio(false); cin.tie(nullptr);
#define BYEBYE return 0;

#define all(cn) (cn).begin(), (cn).end()
#define rep(i, n) for (int i = 0; i < n; ++i)
#define csz(c) ((int)c.size())
#define mp make_pair
#define eb emplace_back
#define fi first
#define se second

#define popcnt __builtin_popcount
#define popcntll __builtin_popcount_ll


const int INFI = 1e9 + 5;
const ll INFL = 1e18 + 5;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count()); 
auto dist = uniform_int_distribution<int>(0, INFI); 
auto distll = uniform_int_distribution<ll>(0, INFL); 
int rnd() { return dist(rng); }
ll rndl() { return distll(rng); }
#define pb pop_back
#define vvc vector<vector<char>>
#define back push_back
using namespace std;

void print(const vvc& partition) {
    for (const auto& subset : partition) {
        cout << "{ ";
        for (char item : subset) {
            cout << item << " ";
        }
        cout << "} ";
    }
    cout << endl;
}
void help(vvc& cp, 
                     const string& elements, int n, int k, int idx) {
    if (idx == n) {
        if (k == 0 || cp.size() == k) {
            print(cp);
        }
        return;
    }
    for (int i = 0; i < cp.size(); ++i) {
        cp[i].back(elements[idx]);
        help(cp, elements, n, k, idx + 1);
        cp[i].pb();
    }
    if (k == 0 || cp.size() < k) {
        cp.back({elements[idx]});
        help(cp, elements, n, k, idx + 1);
        cp.pb();
    }
}

void gen(const string& elements, int k = 0) {
    vvc cp;
    help(cp, elements, elements.size(), k, 0);
}

int main() {
    string elements = "abc";
    gen(elements, 2);
    gen(elements);

    return 0;
}