//Author:xht37
#include <bits/stdc++.h>

#define ui unsigned int
#define ll long long
#define ul unsigned ll
#define ld long double

#define pi pair <int, int>
#define fi first
#define se second
#define mp make_pair

#define ls (p << 1)
#define rs (ls | 1)
#define md ((t[p].l + t[p].r) >> 1)

#define vi vector <int>
#define pb push_back
#define pq priority_queue

#define dbg(x) cerr << #x" = " << x << endl
#define debug(...) fprintf(stderr, __VA_ARGS__)

#define fl(x) freopen(x".in", "r", stdin), freopen(x".out", "w", stdout)

using namespace std;

namespace io {
	const int SI = 1 << 21 | 1;
	char IB[SI], *IS, *IT, OB[SI], *OS = OB, *OT = OS + SI - 1, c, ch[100];
	int f, t;
	#define gc() (IS == IT ? (IT = (IS = IB) + fread(IB, 1, SI, stdin), IS == IT ? EOF : *IS++) : *IS++)
	inline void flush() {
		fwrite(OB, 1, OS - OB, stdout), OS = OB;
	}
	inline void pc(char x) {
		*OS++ = x;
		if (OS == OT) flush();
	}

	template <class I>
	inline void rd(I &x) {
		for (f = 1, c = gc(); c < '0' || c > '9'; c = gc()) if (c == '-') f = -1;
		for (x = 0; c >= '0' && c <= '9'; x = (x << 3) + (x << 1) + (c & 15), c = gc());
		x *= f;
	}
	template <class I>
	inline void rd(I &x, I &y) {
		rd(x), rd(y);
	}
	template <class I>
	inline void rd(I &x, I &y, I &z) {
		rd(x), rd(y), rd(z);
	}
	template <class I>
	inline void rda(I *a, int n) {
		for (int i = 1; i <= n; i++) rd(a[i]);
	}
	inline void rdc(char &c) {
		for (c = gc(); c < 33 || c > 126; c = gc());
	}
	inline void rds(char *s, int &n) {
		for (c = gc(); c < 33 || c > 126; c = gc());
		for (n = 0; c >= 33 && c <= 126; s[++n] = c, c = gc());
		s[n+1] = '\0';
	}
	inline void rds(string &s) {
		for (c = gc(); c < 33 || c > 126; c = gc());
		for (s.clear(); c >= 33 && c <= 126; s.pb(c), c = gc());
	}

	template <class I>
	inline void print(I x, char k = '\n') {
		if (!x) pc('0');
		if (x < 0) pc('-'), x = -x;
		while (x) ch[++t] = x % 10 + '0', x /= 10;
		while (t) pc(ch[t--]);
		pc(k);
	}
	template <class I>
	inline void print(I x, I y) {
		print(x, ' '), print(y);
	}
	template <class I>
	inline void print(I x, I y, I z) {
		print(x, ' '), print(y, ' '), print(z);
	}
	template <class I>
	inline void printa(I *a, int n) {
		for (int i = 1; i <= n; i++) print(a[i], " \n"[i==n]);
	}
	inline void printc(char c) {
		pc(c);
	}
	inline void prints(char *s, int n) {
		for (int i = 1; i <= n; i++) pc(s[i]);
		pc('\n');
	}
	inline void prints(string s) {
		int n = s.length();
		while (t < n) pc(s[t++]);
		pc('\n'), t = 0;
	}
	struct Flush {
		~Flush() {
			flush();
		}
	} flusher;
}
using io::rd;
using io::rda;
using io::rdc;
using io::rds;
using io::print;
using io::printa;
using io::printc;
using io::prints;

const int N = 1e5 + 7;
int n, ans, d[N];
vi e[N];
char s[N];
bool a[N], c[N], b[N];

void dfs1(int x, int fa) {
	b[x] = c[x];
	for (int y : e[x])
		if (y != fa)
			dfs1(y, x), b[x] |= b[y];
	ans += b[x];
	if (!b[x]) a[fa] ^= 1;
}

void dfs2(int x, int fa) {
	d[x] = d[fa] + c[x];
	for (int y : e[x])
		if (b[y] && y != fa)
			dfs2(y, x);
}

int main() {
	rd(n);
	for (int i = 1, x, y; i < n; i++)
		rd(x, y), e[x].pb(y), e[y].pb(x), a[x] ^= 1, a[y] ^= 1;
	rds(s, n);
	int rt = 0;
	for (int i = 1; i <= n; i++) {
		c[i] = s[i] == 'W';
		if (s[i] == 'W') rt = i;
	}
	if (!rt) return prints("0"), 0;
	dfs1(rt, 0);
	ans = ans * 2 - 2;
	if (!ans) return prints("1"), 0;
	for (int i = 1; i <= n; i++)
		if (b[i]) ans += c[i] ^= a[i];
	dfs2(rt, 0);
	for (int i = 1; i <= n; i++)
		if (b[i] && d[i] > d[rt]) rt = i;
	d[rt] = 0, dfs2(rt, 0);
	for (int i = 1; i <= n; i++)
		if (b[i] && d[i] > d[rt]) rt = i;
	print(ans - d[rt] * 2);
	return 0;
}

Measured memory_bytes: 16000