#include using namespace std; typedef signed long long ll; #undef _P #define _P(...) (void)printf(__VA_ARGS__) #define FOR(x,to) for(x=0;x<(to);x++) #define FORR(x,arr) for(auto& x:arr) #define ITR(x,c) for(__typeof(c.begin()) x=c.begin();x!=c.end();x++) #define ALL(a) (a.begin()),(a.end()) #define ZERO(a) memset(a,0,sizeof(a)) #define MINUS(a) memset(a,0xff,sizeof(a)) //------------------------------------------------------- int N; int TC,TW; string S; int CC[101010],CW[101010]; vector E[101010]; ll ret; void dfs(int cur,int pre) { if(S[cur]=='c') CC[cur]=1; if(S[cur]=='w') CW[cur]=1; FORR(e,E[cur]) if(e!=pre) { dfs(e,cur); CC[cur]+=CC[e]; CW[cur]+=CW[e]; if(S[cur]=='w') ret += 1LL*CC[e]*(TW-1-CW[e]); } if(S[cur]=='w') ret += 1LL*(TC-CC[cur])*(CW[cur]-1); } void solve() { int i,j,k,l,r,x,y; string s; cin>>N>>S; FORR(c,S) if(c=='c') TC++; FORR(c,S) if(c=='w') TW++; FOR(i,N-1) { cin>>x>>y; E[x-1].push_back(y-1); E[y-1].push_back(x-1); } dfs(0,-1); cout<