//四則演算 #pragma GCC target("avx") //並列計算 #pragma GCC optimize("O3") //条件分岐を減らす #pragma GCC optimize("unroll-loops") //浮動小数点演算 #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native") #include using namespace std; using ll = long long; using ld = long double; using VI = vector; using VL = vector; using VS = vector; template using PQ = priority_queue, greater>; #define FOR(i,a,n) for(int i=(a);i<(n);++i) #define eFOR(i,a,n) for(int i=(a);i<=(n);++i) #define rFOR(i,a,n) for(int i=(n)-1;i>=(a);--i) #define erFOR(i,a,n) for(int i=(n);i>=(a);--i) #define each(i, a) for(auto &i : a) #define SORT(a) sort(a.begin(),a.end()) #define rSORT(a) sort(a.rbegin(),a.rend()) #define fSORT(a,f) sort(a.begin(),a.end(),f) #define all(a) a.begin(),a.end() #define out(y,x) ((y)<0||h<=(y)||(x)<0||w<=(x)) #define tp(a,i) get(a) #define line cout << "-----------------------------\n" #define ENDL(i,n) ((i) == (n) - 1 ? "\n" : " ") #define stop system("pause") constexpr ll INF = 1000000000; constexpr ll LLINF = 1LL << 60; constexpr ll mod = 1000000007; constexpr ll MOD = 998244353; constexpr ld eps = 1e-10; constexpr ld pi = 3.1415926535897932; templateinline bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; }return false; } templateinline bool chmin(T& a, const T& b) { if (a > b) { a = b; return true; }return false; } inline void init() { cin.tie(nullptr); cout.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(15); } templateinline istream& operator>>(istream& is, vector& v) { for (auto& a : v)is >> a; return is; } templateinline istream& operator>>(istream& is, deque& v) { for (auto& a : v)is >> a; return is; } templateinline istream& operator>>(istream& is, pair& p) { is >> p.first >> p.second; return is; } templateinline vector vec(size_t a) { return vector(a); } templateinline vector defvec(T def, size_t a) { return vector(a, def); } templateinline auto vec(size_t a, Ts... ts) { return vector(ts...))>(a, vec(ts...)); } templateinline auto defvec(T def, size_t a, Ts... ts) { return vector(def, ts...))>(a, defvec(def, ts...)); } templateinline void print(const T& a) { cout << a << "\n"; } templateinline void print(const pair& a) { cout << a.first << " " << a.second << "\n"; } templateinline void print(const T& a, const Ts&... ts) { cout << a << " "; print(ts...); } templateinline void print(const vector& v) { for (int i = 0; i < v.size(); ++i)cout << v[i] << "\n"; } templateinline void print(const vector>& v) { for (auto& a : v)print(a); } templateinline void print(const vector>& v) { for (auto& a : v)print(a); } inline string reversed(const string& s) { string t = s; reverse(all(t)); return t; } pair operator+=(pair& x, const pair& y) { x.first += y.first; x.second += y.second; return x; } pair operator+(pair x, const pair y) { return x += y; } pair operator-=(pair& x, const pair& y) { x.first -= y.first; x.second -= y.second; return x; } pair operator-(pair x, const pair y) { return x -= y; } int main() { init(); int n; cin >> n; string s; cin >> s; vector g(n); FOR(i, 0, n - 1) { int a, b; cin >> a >> b; --a, --b; g[a].push_back(b); g[b].push_back(a); } #define w first #define c second vector> wc(n); { auto dfs = [&](auto&& f, int cur, int par)->void { if (s[cur] == 'w')++wc[cur].w; else ++wc[cur].c; int idx = -1, sz = g[cur].size(); for (int i = 0, to; i < sz; ++i) { to = g[cur][i]; if (to == par)idx = i; else { f(f, to, cur); wc[cur].w += wc[to].w; wc[cur].c += wc[to].c; } } if (idx != -1)g[cur].erase(g[cur].begin() + idx); }; dfs(dfs, 0, -1); } ll ans = 0; { auto dfs = [&](auto&& f, int cur, pair x)->void { int sz = g[cur].size(); vector> l(sz), r(sz); pair y = s[cur] == 'w' ? pair(1LL, 0LL) : pair(0LL, 1LL); for (int i = 0, to; i < sz; ++i) { to = g[cur][i]; if (i < sz - 1)l[i + 1] = wc[to] + l[i]; if (0 < i)r[i - 1] = wc[to]; } rFOR(i, 0, sz - 1)r[i] += r[i + 1]; if (s[cur] == 'w') { ans += x.w * (wc[cur] - y).c; ans += x.c * (wc[cur] - y).w; } for (int i = 0, to; i < sz; ++i) { to = g[cur][i]; f(f, to, x + l[i] + r[i] + y); } }; dfs(dfs, 0, pair()); } print(ans); return 0; }