#include <bits/stdc++.h>
using namespace std;
#define LOCAL
#pragma region Macros
typedef long long ll;
#define ALL(x) (x).begin(),(x).end()
const long long MOD=1000000007;
// const long long MOD=998244353;
const int INF=1e9;
const long long IINF=1e18;
const int dx[4]={1,0,-1,0},dy[4]={0,1,0,-1};
const char dir[4]={'D','R','U','L'};

template<typename T>
istream &operator>>(istream &is,vector<T> &v){
    for (T &x:v) is >> x;
    return is;
}
template<typename T>
ostream &operator<<(ostream &os,const vector<T> &v){
    for (int i=0;i<v.size();++i){
        os << v[i] << (i+1==v.size()?"": " ");
    }
    return os;
}
template<typename T,typename U>
ostream &operator<<(ostream &os,const pair<T,U> &p){
    os << '(' << p.first << ',' << p.second << ')';
    return os;
}
template<typename T,typename U>
ostream &operator<<(ostream &os,const map<T,U> &m){
    os << '{';
    for (auto itr=m.begin();itr!=m.end();++itr){
        os << '(' << itr->first << ',' << itr->second << ')';
        if (++itr!=m.end()) os << ',';
        --itr;
    }
    os << '}';
    return os;
}
template<typename T>
ostream &operator<<(ostream &os,const set<T> &s){
    os << '{';
    for (auto itr=s.begin();itr!=s.end();++itr){
        os << *itr;
        if (++itr!=s.end()) os << ',';
        --itr;
    }
    os << '}';
    return os;
}

void debug_out(){cerr << '\n';}
template<class Head,class... Tail>
void debug_out(Head&& head,Tail&&... tail){
    cerr << head;
    if (sizeof...(Tail)>0) cerr << ", ";
    debug_out(move(tail)...);
}
#ifdef LOCAL
#define debug(...) cerr << " ";\
cerr << #__VA_ARGS__ << " :[" << __LINE__ << ":" << __FUNCTION__ << "]" << '\n';\
cerr << " ";\
debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif

template<typename T> T gcd(T x,T y){return y!=0?gcd(y,x%y):x;}
template<typename T> T lcm(T x,T y){return x/gcd(x,y)*y;}

template<class T1,class T2> inline bool chmin(T1 &a,T2 b){
    if (a>b){a=b; return true;} return false;
}
template<class T1,class T2> inline bool chmax(T1 &a,T2 b){
    if (a<b){a=b; return true;} return false;
}
#pragma endregion

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    int N; cin >> N;
    vector<vector<int>> G(N);
    for (int i=0;i<N-1;++i){
        int x,y; cin >> x >> y; --x,--y;
        G[x].emplace_back(y);
        G[y].emplace_back(x);
    }
    string S; cin >> S;

    vector<int> c(N);
    int r=-1;
    for (int i=0;i<N;++i){
        c[i]=(S[i]=='W');
        if (c[i]) r=i;
    }
    if (r<0){cout << 0 << '\n'; return 0;}

    auto dfs1=[&](auto self,int v,int p)->int{
        int sub_W=c[v];
        for (int i=0;i<G[v].size();++i){
            int u=G[v][i];
            if (u==p) continue;
            if (!self(self,u,v)){
                swap(G[v][i],G[v].back());
                G[v].pop_back();
                --i; continue;
            } else sub_W=1;
        }
        return sub_W;
    };
    vector<int> dp(N,0);
    int es=0,W=0,ans=0;
    auto dfs2=[&](auto self,int v,int p)->void{
        c[v]^=(G[v].size()&1);
        W+=c[v];
        for (int u:G[v]){
            if (u==p) continue;
            self(self,u,v); ++es;
            dp[v]=max(dp[v],dp[u]);
        }
        dp[v]+=c[v];
    };
    auto dfs3=[&](auto self,int v,int p,int D)->void{
        vector<int> ch;
        int s=G[v].size();
        for (int u:G[v]) ch.emplace_back((u==p?D:dp[u]));
        vector<int> left(s+1,0),right(s+1,0);
        for (int i=0;i<s;++i) left[i+1]=max(left[i],ch[i]);
        for (int i=s-1;i>=0;--i) right[i]=max(right[i+1],ch[i]);
        ans=max(ans,left[s]);
        for (int i=0;i<G[v].size();++i){
            int u=G[v][i];
            if (u==p) continue;
            self(self,u,v,max(left[i],right[i+1])+c[v]);
        }
    };
    dfs1(dfs1,r,-1);
    dfs2(dfs2,r,-1);
    dfs3(dfs3,r,-1,0);

    cout << 2*es+W-2*ans << '\n';
}

Measured memory_bytes: 36040