func_code_string: #include <bits/stdc++.h>   using namespace std;   using ll = long long;   template <class t, class u>   void chmax(t& first, u second) {     if (first < second) first = second;   }   template <class t, class u>   void chmin(t& first, u second) {     if (second < first) first = second;   }   template <class t>   using vc = vector<t>;   template <class t>   using vvc = vc<vc<t>>;   using pi = pair<int, int>;   using vi = vc<int>;   template <class t, class u>   ostream& operator<<(ostream& os, const pair<t, u>& p) {     return os <<  {  << p.first <<  ,  << p.second <<  } ;   }   template <class t>   ostream& operator<<(ostream& os, const vc<t>& v) {     os <<  { ;     for (auto e : v) os << e <<  , ;     return os <<  } ;   }   using uint = unsigned;   using ull = unsigned long long;   template <int i, class T>   void print_tuple(ostream&, const T&) {}   template <int i, class T, class H, class... Args>   void print_tuple(ostream& os, const T& t) {     if (i) os <<  , ;     os << get<i>(t);     print_tuple<i + 1, T, Args...>(os, t);   }   template <class... Args>   ostream& operator<<(ostream& os, const tuple<Args...>& t) {     os <<  { ;     print_tuple<0, tuple<Args...>, Args...>(os, t);     return os <<  } ;   }   void print(ll x, int suc = 1) {     cout << x;     if (suc == 1) cout <<   n ;     if (suc == 2) cout <<    ;   }   ll read() {     ll i;     cin >> i;     return i;   }   vi readvi(int n, int off = 0) {     vi v(n);     for (int i = int(0); i < int(n); i++) v[i] = read() + off;     return v;   }   template <class T>   void print(const vector<T>& v, int suc = 1) {     for (int i = int(0); i < int(v.size()); i++)       print(v[i], i == int(v.size()) - 1 ? suc : 2);   }   string readString() {     string s;     cin >> s;     return s;   }   template <class T>   T sq(const T& t) {     return t * t;   }   void yes(bool ex = true) {     cout <<  Yes  << endl;     if (ex) exit(0);   }   void no(bool ex = true) {     cout <<  No  << endl;     if (ex) exit(0);   }   constexpr ll ten(int n) { return n == 0 ? 1 : ten(n - 1) * 10; }   const ll infLL = LLONG_MAX / 3;   const int inf = INT_MAX / 2 - 100;   int topbit(signed t) { return t == 0 ? -1 : 31 - __builtin_clz(t); }   int topbit(ll t) { return t == 0 ? -1 : 63 - __builtin_clzll(t); }   int botbit(signed first) { return first == 0 ? 32 : __builtin_ctz(first); }   int botbit(ll first) { return first == 0 ? 64 : __builtin_ctzll(first); }   int popcount(signed t) { return __builtin_popcount(t); }   int popcount(ll t) { return __builtin_popcountll(t); }   bool ispow2(int i) { return i && (i & -i) == i; }   int mask(int i) { return (int(1) << i) - 1; }   bool inc(int first, int second, int c) {     return first <= second && second <= c;   }   template <class t>   void mkuni(vc<t>& v) {     sort(v.begin(), v.end());     v.erase(unique(v.begin(), v.end()), v.end());   }   ll rand_int(ll l, ll r) {     static random_device rd;     static mt19937_64 gen(rd());     return uniform_int_distribution<ll>(l, r)(gen);   }   template <class t>   int lwb(const vc<t>& v, const t& first) {     return lower_bound(v.begin(), v.end(), first) - v.begin();   }   using uint = unsigned;   using ull = unsigned long long;   const uint mod = 998244353;   struct mint {     uint v;     mint(ll vv = 0) { s(vv % mod + mod); }     mint& s(uint vv) {       v = vv < mod ? vv : vv - mod;       return *this;     }     mint operator-() const { return mint() - *this; }     mint& operator+=(const mint& rhs) { return s(v + rhs.v); }     mint& operator-=(const mint& rhs) { return s(v + mod - rhs.v); }     mint& operator*=(const mint& rhs) {       v = ull(v) * rhs.v % mod;       return *this;     }     mint& operator/=(const mint& rhs) { return *this *= rhs.inv(); }     mint operator+(const mint& rhs) const { return mint(*this) += rhs; }     mint operator-(const mint& rhs) const { return mint(*this) -= rhs; }     mint operator*(const mint& rhs) const { return mint(*this) *= rhs; }     mint operator/(const mint& rhs) const { return mint(*this) /= rhs; }     mint pow(int n) const {       mint res(1), x(*this);       while (n) {         if (n & 1) res *= x;         x *= x;         n >>= 1;       }       return res;     }     mint inv() const { return pow(mod - 2); }     friend ostream& operator<<(ostream& os, const mint& m) { return os << m.v; }     bool operator<(const mint& r) const { return v < r.v; }     bool operator==(const mint& r) const { return v == r.v; }   };   const int vmax = (1 << 21) + 10;   mint fact[vmax], finv[vmax], invs[vmax];   void initfact() {     fact[0] = 1;     for (int i = int(1); i < int(vmax); i++) {       fact[i] = fact[i - 1] * i;     }     finv[vmax - 1] = fact[vmax - 1].inv();     for (int i = vmax - 2; i >= 0; i--) {       finv[i] = finv[i + 1] * (i + 1);     }     for (int i = vmax - 1; i >= 1; i--) {       invs[i] = finv[i] * fact[i - 1];     }   }   mint choose(int n, int k) { return fact[n] * finv[n - k] * finv[k]; }   mint binom(int first, int second) {     return fact[first + second] * finv[first] * finv[second];   }   mint catalan(int n) {     return binom(n, n) - (n - 1 >= 0 ? binom(n - 1, n + 1) : 0);   }   const int nmax = 4010;   const int K = 40;   vi t[nmax];   mint dp[nmax][K];   vc<mint> buf;   mint work[K][K];   void dfs(int v, int p) {     for (auto c : t[v])       if (c != p) dfs(c, v);     memset(work, 0, sizeof(work));     work[0][0] = 1;     for (int us = int(0); us < int(K - 1); us++) {       for (auto c : t[v])         if (c != p) {           for (int i = int(0); i < int(K); i++) {             for (int j = int(0); j < int(K - i - 1); j++) {               work[us + 1][i + j + 1] += work[us][i] * dp[c][j];             }           }         }     }     buf[0] += 1;     for (int us = int(0); us < int(K); us++)       for (int i = int(0); i < int(K); i++) dp[v][i] += work[us][i];     for (int us = int(1); us < int(K); us++) {       for (int i = int(1); i < int(K); i++)         if (work[us][i].v) {           for (int j = int(2); j < int(min((K - 1) / us, (K - 1) / i) + 1); j++) {             work[us * j][i * j] -= work[us][i];           }           for (int j = int(1); j < int(min((K - 1) / us, (K - 1) / i) + 1); j++) {             buf[i * j] += work[us][i] * i * 2 * invs[us];           }         }     }   }   signed main() {     cin.tie(0);     ios::sync_with_stdio(0);     cout << fixed << setprecision(20);     initfact();     int n[2];     for (int i = int(0); i < int(2); i++) cin >> n[i];     int k;     cin >> k;     if (k % 2) {       cout << 0 << endl;       return 0;     }     k /= 2;     vc<mint> x[2];     for (int w = int(0); w < int(2); w++) {       for (int i = int(0); i < int(n[w]); i++) t[i].clear();       memset(dp, 0, sizeof(dp));       buf.assign(K, 0);       for (int _ = int(0); _ < int(n[w] - 1); _++) {         int first, second;         cin >> first >> second;         first--;         second--;         t[first].push_back(second);         t[second].push_back(first);       }       dfs(0, -1);       x[w] = buf;     }     void(0);     void(0);     mint ans = 0;     for (int i = int(0); i < int(k + 1); i++) {       ans += x[0][i] * x[1][k - i] * choose(k * 2, i * 2);     }     cout << ans << endl;   }   