#include "bits/stdc++.h"
#define YESNO OUT(three(solve(),"YES","NO"))
#define YesNo OUT(three(solve(),"Yes","No"))
#define WL(A,B) OUT(three(solve(),A,B))
#define ECHO OUT(solve())
#define three(A,B,C) ((A)?(B):(C))
#define FOR(i,a,b)  for(LL i=(a);i< (LL)(b);i++)
#define EFOR(i,a,b) for(LL i=(a);i<=(LL)(b);i++)
#define RFOR(i,a,b) for(LL i=(b);i>=(LL)(a);i--)
#define REP(i,b) FOR(i,zero,b)
#define rep REP
#define EREP(i,b) EFOR(i,zero,b)
#define RREP(i,b) RFOR(i,b,zero)
#define ALL(c) c.begin(),c.end()
#define UNIQUE(c) sort(ALL(c));c.erase(unique(ALL(c)),c.end())
#define MAX(c) (*max_element(ALL(c)))
#define MIN(c) (*min_element(ALL(c)))
#define MP make_pair
#define FI first
#define SE second
#define SI(x) (LL(x.size()))
#define PB push_back
#define DEBUG(a) OUT(a)
#define DEBUG2(a,b) OUT2(a,b)
#define cat cout << __LINE__ << endl
#define OUT(a) cout << (a) << endl
#define OUT2(a,b) cout << (a) <<" "<<(b) << endl
#define zero 0LL
#define all ALL
#define pb emplace_back
#define eb pb
#define int long long
using namespace std;
template<typename T> inline void maximize(T &a, T b) { a = max(a, b); }
template<typename T> inline void minimize(T &a, T b) { a = min(a, b); }
template<typename T> inline bool middle(T a, T b, T c) { return b <= a && a <= c; }
template<class T> inline bool MX(T &l, const T &r) { return l < r ? l = r, 1 : 0; }
template<class T> inline bool MN(T &l, const T &r) { return l > r ? l = r, 1 : 0; }
template<class T> inline bool chmax(int a, int b, T c, T d) { return c > d ? a : b; }
template<class T> inline bool chmin(int a, int b, T c, T d) { return c > d ? a : b; }
typedef int LL;
typedef double ld;
typedef int ut;
typedef vector<ut> VI;
typedef vector<VI> VII;
typedef pair<ut, ut> pr;
typedef pair<ut, pr> ppr;
typedef vector<pr> Vpr;
typedef vector<ppr> Vppr;
typedef tuple<int, int, int, int> tapu;
typedef vector<tapu> Vtapu;
typedef priority_queue<ppr, Vppr > PQ;
inline void outputVI(VI x) { REP(i, SI(x)) { cout << three(i, " ", "") << x[i]; }OUT(""); }
const int SIZE1 = 1e6 + 1000;
const int SIZE2 = 2012;
const int SIZE3 = 430;
const int SIZE = SIZE1;
const LL p = 998244353;
const LL INF = 1LL << 30;
const long double EPS = 1e-7;
const LL inf = 1000000000;
typedef pair<ld, ut> pld;
const int dx[] = { 0,1,0,-1 }, dy[] = { 1,0,-1,0 };
ut N, M, K, L, Q, H, W, R;
VI edges[SIZE];
LL vals[SIZE], answer = zero;
LL maps[SIZE2][SIZE2];
const LL C = 3;
LL A[SIZE], B[SIZE], D[SIZE], E[SIZE];
LL DP[SIZE][3];
bool checked[SIZE][3];
bool needed[SIZE];
LL needs[SIZE];
LL solve2(int now,int from,int used) {
	if (!needed[now]) return 0;
	assert(needs[now] > 0);
	if (needs[now] == 1 and from!=-1) {
		if (used == 2) return INF;
		return 1;
	}
	if (checked[now][used]) return DP[now][used];
	checked[now][used]=true;
	VI diff,diff2;
	LL ans = 0;
	for (auto next : edges[now]) {
		if (next == from) continue;
		if (!needed[next]) continue;
		ans += solve2(next, now, 0);
		diff.pb(solve2(next, now, 1)-solve2(next, now, 0));
		diff2.pb(solve2(next, now, 2)-solve2(next,now,0));
	}
	diff.pb(INF);
	diff.pb(INF);
	diff2.pb(INF);
	sort(ALL(diff));
	sort(ALL(diff2));
	LL isMatched[] = { ((A[now] % 2) ^ (needs[now] % 2)) ,((A[now] % 2) ^ ((needs[now] - 1) % 2)) };
	LL val[2];
	REP(i, 2) val[i] = ans + needs[now] - i + isMatched[i];
	LL minium = INF;

	if (from == -1 and needs[now]==1) {
		MN(minium, ans + diff[0]+1);
	}
	if (used == 0) MN(minium, val[0]);
	else if (used == 1) MN(minium,diff.front()+val[1]);
	else if (used == 2) {
		MN(minium, diff2.front()+val[0]);
		MN(minium, diff[0]+diff[1] +val[1]);
	}
	return DP[now][used] = minium;
}
LL dfs(int now, int from) {
	needed[now] = A[now];
	for (auto next : edges[now]) {
		if (next == from) continue;
		needed[now] |= dfs(next, now);
	}
	return needed[now];
	
}
LL solve() {
	cin >> N;
	REP(i, N-1) {
		int a, b;
		cin >> a >> b;
		a--;
		b--;
		edges[a].pb(b);
		edges[b].pb(a);
	}
	string s;
	cin >> s;
	LL ws = 0;
	REP(i, N) {
		A[i] = s[i] == 'W';
		ws += A[i];
	}
	if (ws == 0) return 0;
	if (ws == 1) return 1;
	REP(i, N) {
		if (A[i]) {
			dfs(i,-1);
			break;
		}
	}
	REP(i, N) {
		for (auto next : edges[i]) {
			if (needed[next]) needs[i] ++;
		}
	}
	REP(i, N) {
		if (A[i] and needs[i]==1) {
			LL ans= solve2(i, -1, 2);
			assert(abs(ans) <= INF / 2);
			return ans;
		}	
	}
	return 0;
}




//!!!!!!!!!!!!!!!!!!!実装を詰める!!!!!!!!!!!!!!!!!!!!!!!!!
signed main() {

	ios_base::sync_with_stdio(false);
	cout << fixed << setprecision(0);
	cout << solve() <<endl; 
	//cin >> N;
	return 0;

}


Measured memory_bytes: 57296