#include <bits/stdc++.h>

using namespace std;
using ll = long long;
// #define int ll
using PII = pair<ll, ll>;

#define FOR(i, a, n) for (ll i = (ll)a; i < (ll)n; ++i)
#define REP(i, n) FOR(i, 0, n)
#define ALL(x) x.begin(), x.end()

template<typename T> T &chmin(T &a, const T &b) { return a = min(a, b); }
template<typename T> T &chmax(T &a, const T &b) { return a = max(a, b); }
template<typename T> bool IN(T a, T b, T x) { return a<=x&&x<b; }
template<typename T> T ceil(T a, T b) { return a/b + !!(a%b); }

template<typename T> vector<T> make_v(size_t a) { return vector<T>(a); }
template<typename T,typename... Ts>
auto make_v(size_t a,Ts... ts) {
    return vector<decltype(make_v<T>(ts...))>(a,make_v<T>(ts...));
}
template<typename T,typename V> typename enable_if<is_class<T>::value==0>::type
fill_v(T &t, const V &v) { t=v; }
template<typename T,typename V> typename enable_if<is_class<T>::value!=0>::type
fill_v(T &t, const V &v ) { for(auto &e:t) fill_v(e,v); }

template<class S,class T>
ostream &operator <<(ostream& out,const pair<S,T>& a) {
    out<<'('<<a.first<<','<<a.second<<')'; return out;
}
template<class T>
ostream &operator <<(ostream& out,const vector<T>& a){
    out<<'[';
    for(const T &i: a) out<<i<<',';
    out<<']';
    return out;
}
template<class T>
ostream &operator <<(ostream& out, const set<T>& a) {
    out<<'{';
    for(const T &i: a) out<<i<<',';
    out<<'}';
    return out;
}
template<class T, class S>
ostream &operator <<(ostream& out, const map<T,S>& a) {
    out<<'{';
    for(auto &i: a) out<<i<<',';
    out<<'}';
    return out;
}

int dx[] = {0, 1, 0, -1}, dy[] = {1, 0, -1, 0}; // DRUL
const int INF = 1<<30;
const ll LLINF = 1LL<<60;
const ll MOD = 1000000007;

signed main(void)
{
    cin.tie(0);
    ios::sync_with_stdio(false);

    ll n;
    cin >> n;
    vector<vector<ll>> g0(n);
    REP(i, n-1) {
        ll x, y;
        cin >> x >> y;
        x--, y--;
        g0[x].push_back(y);
        g0[y].push_back(x);
    }
    string s;
    cin >> s;
    vector<ll> col(n);
    REP(i, n) col[i] = s[i]=='W';

    // 葉が黒なら削るを繰り返す
    vector<vector<ll>> g;
    {
        vector<bool> del(n);
        vector<ll> deg(n);
        REP(i, n) deg[i] = g0[i].size();
        stack<ll> st;
        REP(i, n) if(deg[i]==1 && col[i]==0) st.push(i);
        while(st.size()) {
            ll t = st.top(); st.pop();
            del[t] = true;
            for(auto to: g0[t]) {
                deg[to]--;
                if(deg[to]==1 && col[to]==0) st.push(to);
            }
        }
        ll idx = 0;
        map<ll,ll> mp;
        REP(i, n) if(!del[i]) mp[i] = idx++;
        vector<ll> n_col;
        REP(i, n) if(!del[i]) n_col.push_back(col[i]);
        col = n_col;
        g.resize(idx);
        REP(i, n) {
            if(del[i]) continue;
            for(auto to: g0[i]) {
                if(del[to]) continue;
                g[mp[i]].push_back(mp[to]);
            }
        }
        n = idx;
    }

    if(n == 0) {
        cout << 0 << endl;
        return 0;
    }
    if(n == 1) {
        if(col[0]==0) cout << 0 << endl;
        else cout << 1 << endl;
        return 0;
    }

    // cout << "col=" << col << endl;
    // REP(i, n) cout << g[i] << endl;

    ll ma = -1, idx = -1;
    function<void(ll,ll,ll)> dfs = [&](ll v, ll p, ll c) {
        if(ma < c) ma = c, idx = v;
        for(auto to: g[v]) if(to != p) {
            ll cond = col[v] ^ (g[v].size()%2);
            dfs(to, v, c + cond);
        }
    };
    dfs(0, -1, col[0] ^ (g[0].size()%2));
    ma = -1;
    dfs(idx, -1, col[idx] ^ (g[idx].size()%2));
    ll num = 0;
    REP(i, n) num += col[i] ^ (g[i].size()%2);
    cout << 2*(n-1) + num - ma*2 << endl;

    return 0;
}


Measured memory_bytes: 29224