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<ll, ll>;   using vi = vc<ll>;   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 <class t, size_t n>   ostream& operator<<(ostream& os, const array<t, n>& first) {     return os << vc<t>(first.begin(), first.end());   }   template <ll i, class T>   void print_tuple(ostream&, const T&) {}   template <ll 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 <<  } ;   }   template <class t>   void print(t x, ll suc = 1) {     cout << x;     if (suc == 1) cout <<   n ;     if (suc == 2) cout <<    ;   }   ll read() {     ll i;     cin >> i;     return i;   }   vi readvi(ll n, ll off = 0) {     vi v(n);     for (ll i = ll(0); i < ll(n); i++) v[i] = read() + off;     return v;   }   template <class T>   void print(const vector<T>& v, ll suc = 1) {     for (ll i = ll(0); i < ll(v.size()); i++)       print(v[i], i == ll(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           <<   n ;     if (ex) exit(0);   }   void no(bool ex = true) {     cout <<  No           <<   n ;     if (ex) exit(0);   }   void possible(bool ex = true) {     cout <<  Possible           <<   n ;     if (ex) exit(0);   }   void impossible(bool ex = true) {     cout <<  Impossible           <<   n ;     if (ex) exit(0);   }   constexpr ll ten(ll n) { return n == 0 ? 1 : ten(n - 1) * 10; }   const ll infLL = LLONG_MAX / 3;   const ll inf = infLL;   ll topbit(signed t) { return t == 0 ? -1 : 31 - __builtin_clz(t); }   ll topbit(ll t) { return t == 0 ? -1 : 63 - __builtin_clzll(t); }   ll botbit(signed first) { return first == 0 ? 32 : __builtin_ctz(first); }   ll botbit(ll first) { return first == 0 ? 64 : __builtin_ctzll(first); }   ll popcount(signed t) { return __builtin_popcount(t); }   ll popcount(ll t) { return __builtin_popcountll(t); }   bool ispow2(ll i) { return i && (i & -i) == i; }   ll mask(ll i) { return (ll(1) << i) - 1; }   bool inc(ll first, ll second, ll 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 mt19937_64 gen(chrono::steady_clock::now().time_since_epoch().count());     return uniform_int_distribution<ll>(l, r)(gen);   }   template <class t>   void myshuffle(vc<t>& first) {     for (ll i = ll(0); i < ll(ll(first.size())); i++)       swap(first[i], first[rand_int(0, i)]);   }   template <class t>   ll lwb(const vc<t>& v, const t& first) {     return lower_bound(v.begin(), v.end(), first) - v.begin();   }   template <class N, class E>   struct treedp {     const vvc<E>& g;     vc<N> first, second, res, sub, bus;     void dfs1(ll v, ll p) {       first[v].init(v);       E up;       for (auto e : g[v])         if (e != p) {           dfs1(e, v);           second[e] = first[v];           first[v] = first[v] + first[e];         } else           up = e;       sub[v] = first[v];       if (p != -1) first[v] = first[v].up(up);     }     void dfs2(ll v, ll p, N cur) {       for (ll i = ll(g[v].size()) - 1; i >= ll(0); i--) {         auto e = g[v][i];         if (e == p) continue;         void(0);         bus[e] = cur + second[e];         bus[e].show();         dfs2(e, v, bus[e].up(e));         cur = cur + first[e];       }       res[v] = cur;     }     treedp(const vvc<E>& gg)         : g(gg),           first(ll(g.size())),           second(ll(g.size())),           res(ll(g.size())),           sub(ll(g.size())),           bus(ll(g.size())) {       dfs1(0, -1);       N tmp;       tmp.init(0);       dfs2(0, -1, tmp);     }   };   struct N {     signed v[2][2], s;     void init(ll) {       v[0][0] = 1;       v[0][1] = 0;       v[1][0] = 0;       v[1][1] = 0;       s = 1;     }     N up(ll) const {       N res{};       res.v[0][0] = v[1][0];       res.v[0][1] = v[0][0] + v[1][1];       res.v[1][0] = v[0][0];       res.v[1][1] = v[0][1];       res.s = s + 1;       return res;     }     N operator+(const N& r) const {       show();       r.show();       N res{};       for (ll first = ll(0); first < ll(2); first++)         for (ll second = ll(0); second < ll(2 - first); second++) {           for (ll c = ll(0); c < ll(2); c++)             for (ll d = ll(0); d < ll(2 - c); d++) {               res.v[first + second][c + d] += v[first][c] * r.v[second][d];             }         }       res.s = s + r.s - 1;       return res;     }     ll get() { return v[0][0] + v[1][1]; }     ll get2() { return v[1][0] * s; }     void show() const {       for (ll i = ll(0); i < ll(2); i++)         for (ll j = ll(0); j < ll(2); j++) void(0);     }   };   signed main() {     cin.tie(0);     ios::sync_with_stdio(0);     cout << fixed << setprecision(20);     ll n;     cin >> n;     vvc<ll> t(n);     for (ll i = ll(0); i < ll(n - 1); i++) {       ll first, second;       cin >> first >> second;       first--;       second--;       t[first].push_back(second);       t[second].push_back(first);     }     treedp<N, ll> dp(t);     ll ans = 0;     for (ll i = ll(1); i < ll(n); i++) {       dp.sub[i].show();       dp.bus[i].show();       ans += dp.sub[i].get() * dp.bus[i].get();       ans += dp.sub[i].get2() * dp.bus[i].get2();     }     print(ans);   }   