#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #ifdef LOCAL # include "debug_print.hpp" # define debug(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__) #else # define debug(...) (static_cast(0)) #endif using namespace std; #define rep(i,n) for(int i=0; i<(n); i++) #define rrep(i,n) for(int i=(n)-1; i>=0; i--) #define FOR(i,a,b) for(int i=(a); i<(b); i++) #define RFOR(i,a,b) for(int i=(b-1); i>=(a); i--) #define ALL(v) v.begin(), v.end() #define RALL(v) v.rbegin(), v.rend() #define UNIQUE(v) v.erase( unique(v.begin(), v.end()), v.end() ); #define pb push_back using ll = long long; using D = double; using LD = long double; using P = pair; template using PQ = priority_queue>; template using minPQ = priority_queue, greater>; templatebool chmax(T &a, const T &b) { if (abool chmin(T &a, const T &b) { if (b ostream &operator<<(ostream &os, const pair &p) { os << p.first << " " << p.second; return os; } template istream &operator>>(istream &is, pair &p) { is >> p.first >> p.second; return is; } template ostream &operator<<(ostream &os, const vector &v) { int s = (int)v.size(); for (int i = 0; i < s; i++) os << (i ? " " : "") << v[i]; return os; } template istream &operator>>(istream &is, vector &v) { for (auto &x : v) is >> x; return is; } void in() {} template void in(T &t, U &...u) { cin >> t; in(u...); } void out() { cout << "\n"; } template void out(const T &t, const U &...u) { cout << t; if (sizeof...(u)) cout << sep; out(u...); } void outr() {} template void outr(const T &t, const U &...u) { cout << t; outr(u...); } const int MAX_N = 100005; string s; vector g[MAX_N]; struct var { ll cnt, sz; var(ll cnt = 0, ll sz = 0): cnt(cnt), sz(sz) {} var operator+ (const var& a) const { return {cnt+a.cnt, sz+a.sz}; } var addRoot(int v) const { if(s[v] == 'w'){ return {cnt+sz, sz+1}; } else{ return *this; } } }; vector dp[MAX_N]; var ans[MAX_N]; var dfs1(int v, int p = -1) { var dpsum; dp[v] = vector (g[v].size()); rep(i, g[v].size()) { int u = g[v][i]; if(u == p) continue; dp[v][i] = dfs1(u, v); dpsum = dpsum + dp[v][i]; } return dpsum.addRoot(v); } void dfs2(int v, const var& dpParent = var(), int p = -1) { int deg = g[v].size(); rep(i, deg) if(g[v][i] == p) dp[v][i] = dpParent; vector dpSum_Left(deg+1), dpSum_Right(deg+1); rep(i,deg) dpSum_Left[i+1] = dpSum_Left[i] + dp[v][i]; rrep(i, deg) dpSum_Right[i] = dpSum_Right[i+1] + dp[v][i]; ans[v] = dpSum_Left[deg].addRoot(v); rep(i,deg) { int u = g[v][i]; if(u == p) continue; var d = dpSum_Left[i] + dpSum_Right[i+1]; dfs2(u, d.addRoot(v), v); } } int main(){ ios_base::sync_with_stdio(false); cin.tie(nullptr); int n; cin >> n >> s; rep(i,n-1) { int a,b; cin >> a >> b; a--; b--; g[a].pb(b); g[b].pb(a); } dfs1(0); dfs2(0); ll res = 0; rep(i,n){ if(s[i] == 'c') res += ans[i].cnt; } out(res); }