#include<bits/stdc++.h>
using namespace std;


#define li          long long int
#define rep(i,to)   for(li i=0;i<((li)(to));i++)
#define repp(i,start,to)    for(li i=(li)(start);i<((li)(to));i++)
#define pb          push_back
#define sz(v)       ((li)(v).size())
#define bgn(v)      ((v).begin())
#define eend(v)     ((v).end())
#define allof(v)    (v).begin(), (v).end()
#define dodp(v,n)       memset(v,(li)n,sizeof(v))
#define bit(n)      (1ll<<(li)(n))
#define mp(a,b)     make_pair(a,b)
#define rin rep(i,n)
#define EPS 1e-12
#define ETOL 1e-8
#define MOD 1000000007
typedef pair<li, li> PI;

#define INF bit(60)

#define DBGP 1


#define idp if(DBGP)
#define F first
#define S second
#define p2(a,b)     idp cout<<a<<"\t"<<b<<endl
#define p3(a,b,c)       idp cout<<a<<"\t"<<b<<"\t"<<c<<endl
#define p4(a,b,c,d)     idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<endl
#define p5(a,b,c,d,e)       idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<endl
#define p6(a,b,c,d,e,f)     idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<endl
#define p7(a,b,c,d,e,f,g)       idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<"\t"<<g<<endl
#define p8(a,b,c,d,e,f,g,h)     idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<"\t"<<g<<"\t"<<h<<endl
#define p9(a,b,c,d,e,f,g,h,i)       idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<"\t"<<g<<"\t"<<h<<"\t"<<i<<endl
#define p10(a,b,c,d,e,f,g,h,i,j)        idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<"\t"<<g<<"\t"<<h<<"\t"<<i<<"\t"<<j<<endl
#define foreach(it,v)   for(__typeof((v).begin()) it=(v).begin(); it!=(v).end(); ++it)
#define p2p(x)      idp p2((x).F, (x).S)
#define dump(x,n)   idp{rep(i,n){cout<<x[i]<<" ";}puts("");}
#define dump2(x,n)  idp{rep(i,n){cout<<"["<<x[i].F<<" , "<<x[i].S<<"] ";}puts("");}
#define dumpi(x)    idp{foreach(it, x){cout<<(*it)<<" ";}puts("");}
#define dumpi2(x)   idp{foreach(it, x){cout<<"["<<(it)->F<<" , "<<(it)->S<<"] ";}puts("");}

#define read2d(a,w,h)   rep(i,h)rep(j,w)cin>>a[i][j]
#define dump2d(a,w,h)   rep(i,h){rep(j,w)cout<<a[i][j]<<" ";puts("");}

typedef pair<li, li> PI;


li n;
vector<li> edge_org[100100];
vector<li> edge[100100];

bool is_white[100100];
bool cost[100100];

// returns true iff subtree from now has at least 1 white child.
inline bool recur(li now, li from) {
    bool res = is_white[now];
    rep(i, sz(edge_org[now])) {
        li next = edge_org[now][i];
        if (next == from)continue;
        bool tres = recur(next, now);
        res = res || tres;
        if (tres) {
            edge[now].pb(next);
            edge[next].pb(now);
        }
    }
    return res;
}

inline void make_graph() {
    rin{
        if (is_white[i]) {
            recur(i, -1);
            return;
        }
    }
}

PI dfs(li now, li from) {
    PI res(cost[now], now);
    rep(i, sz(edge[now])) {
        li next = edge[now][i];
        if (next == from)continue;
        PI tres = dfs(next, now);
        if (tres.F >= res.F) {
            res = tres;
            if (cost[now])res.F++;
        }
    }
    return res;
}

int main() {
    cin >> n;
    rep(i, n - 1) {
        li x, y;
        cin >> x >> y;
        x--;
        y--;
        edge_org[x].pb(y);
        edge_org[y].pb(x);
    }
    string s;
    cin >> s;
    li white_num = 0;
    rin{
        is_white[i] = (s[i] == 'W');
        if (s[i] == 'W') {
            ++white_num;
        }
    }
    if (white_num <= 1) {
        cout << white_num << endl;
        return 0;
    }
    make_graph();

    li total_edge_num = 0;
    li total_cost_num = 0;
    li tmp_start = -1;
    rin{
        total_edge_num += sz(edge[i]);
        if (sz(edge[i]) > 0) {
            tmp_start = i;
        }
        cost[i] = ((sz(edge[i]) % 2 > 0) ^ (is_white[i]));
        if (cost[i])++total_cost_num;

        //dumpi(edge[i]);
    }

    PI dfs_first = dfs(tmp_start, -1);
    PI dfs_second = dfs(dfs_first.S, -1);

    //dump(cost, n);
    //p3(total_edge_num, total_cost_num, dfs_second.F);
    cout << total_edge_num + total_cost_num - dfs_second.F * 2 << endl;

    return 0;
}

Measured memory_bytes: 19328