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

using SS = int;
class SegmentTree{
    public:
    int siz = 1,n;
    vector<SS> dat;
 
    SS op(SS a, SS b){return a+b;}
    SS e(){return 0;}
    void renew (SS &a,SS x){
        a = op(a,x);
        //a = x;
        //その他.
    }
 
    void make(int N){
        while(siz < N) siz *= 2;
        n = N; dat.resize(siz*2,e());
    }
 
    void make2(int N,vector<SS> &A){
        make(N);
        for(int i=0; i<N; i++){
            int pos = i+siz;
            dat.at(pos) = A.at(i);
        }
        for(int i=siz-1; i>0; i--) dat.at(i) = op(dat.at(i*2),dat.at(i*2+1));
    }
 
    void update(int pos,SS x){
        pos = pos+siz;
        renew(dat.at(pos),x);
        while(pos != 1){
            pos = pos/2;
            dat.at(pos) = op(dat.at(pos*2),dat.at(pos*2+1));
        }
    }
 
    SS findans(int l, int r){
        SS retl = e(),retr = e();
        l += siz,r += siz;
        while(l < r){
            if(l&1) retl = op(retl,dat.at(l++));
            if(r&1) retr = op(dat.at(--r),retr);
            l >>= 1; r >>= 1;
        }
        return op(retl,retr);
    }
 
    SS get(int pos){return dat.at(pos+siz);}
    SS rangeans(int l, int r){return findans(l,r);}
    SS allrange(){return dat.at(1);}
 
    //rightは) leftは[で 渡す&返す. 
    int maxright(const function<bool(SS)> f,int l = 0){
        l += siz; int r = n+siz;
        vector<int> ls,rs;
        while(l < r){
            if(l&1) ls.push_back(l++);
            if(r&1) rs.push_back(--r);
            l >>= 1; r >>= 1; 
        }
        SS okl = e();
        for(int i=0; i<ls.size(); i++){
            l = ls.at(i);
            SS now = op(okl,dat.at(l));
            if(!f(now)){
                while(l < siz){
                    l <<= 1;
                    now = op(okl,dat.at(l));
                    if(f(now)){okl = now; l++;}
                }
                return l-siz;
            } 
            okl = now;
        }
        for(int i=rs.size()-1; i>=0; i--){
            l = rs.at(i);
            SS now = op(okl,dat.at(l));
            if(!f(now)){
                while(l < siz){
                    l <<= 1;
                    now = op(okl,dat.at(l));
                    if(f(now)){okl = now; l++;}
                }
                return l-siz;
            } 
            okl = now;
        }
        return n;
    }
    int minleft(const function<bool(SS)> f,int r = -1){
        if(r == -1) r = n;
        int l = siz; r += siz;
        vector<int> ls,rs;
        while(l < r){
            if(l&1) ls.push_back(l++);
            if(r&1) rs.push_back(--r);
            l >>= 1; r >>= 1; 
        }
        SS okr = e();
        for(int i=0; i<rs.size(); i++){
            r = rs.at(i);
            SS now = op(dat.at(r),okr);
            if(!f(now)){
                while(r < siz){
                    r <<= 1; r++;
                    now = op(dat.at(r),okr);
                    if(f(now)){okr = now; r--;}
                }
                return r+1-siz;
            }
        }
        for(int i=ls.size()-1; i>=0; i--){
            r = ls.at(i);
            SS now = op(dat.at(r),okr);
            if(!f(now)){
                while(r < siz){
                    r <<= 1; r++;
                    now = op(dat.at(r),okr);
                    if(f(now)){okr = now; r--;}
                }
                return r+1-siz;
            }
        }
        return 0;
    }
    //ノーマルセグ木.一年の時を経て漸く二分探索実装した.
};

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int N; cin >> N;
    vector<vector<int>> Graph(N);
    for(int i=0; i<N-1; i++){
        int u,v; cin >> u >> v;
        u--; v--;
        Graph.at(u).push_back(v);
        Graph.at(v).push_back(u);
    }
    vector<int> siz(N);
    {
        auto dfs = [&](auto dfs,int pos,int back) -> int {
            int ret = 1;
            for(auto to : Graph.at(pos)) if(to != back) ret += dfs(dfs,to,pos);
            siz.at(pos) = ret; return ret;
        };
        dfs(dfs,0,-1);
    }
    for(auto &g : Graph) sort(g.begin(),g.end(),[&](auto &a,auto &b){return siz.at(a)>siz.at(b);});

    SegmentTree Z; Z.make(N*2+9);
    int zero = N+4;

    long long answer = 0;
    string s; cin >> s;

    auto dfs = [&](auto dfs,int pos,int back) -> int {
        int maxs = 0,big = -1;
        for(auto to : Graph.at(pos)) if(to != back && maxs < siz.at(to)) maxs = siz.at(to),big = to;
        for(auto to : Graph.at(pos)){
            if(to == back || to == big) continue;
            int n = dfs(dfs,to,pos);
            auto dfs2 = [&](auto dfs2,int pos,int back) -> void {
                if(s.at(pos) == '1') n++;
                else n--;
                Z.update(n,-1);
                for(auto to : Graph.at(pos)) if(to != back) dfs2(dfs2,to,pos);
                if(s.at(pos) == '1') n--;
                else n++;
            };
            dfs2(dfs2,to,pos);
        }
        {
            int n = zero;
            if(big != -1) n = dfs(dfs,big,pos);
            Z.update(n,1);
            if(s.at(pos) == '1') n--;
            else n++;
            answer += Z.rangeans(n+1,Z.siz);
            auto dfs2 = [&](auto dfs2,int pos,int back) -> void {
                if(s.at(pos) == '1') n--;
                else n++;
                answer += Z.rangeans(n+1,Z.siz);
                for(auto to : Graph.at(pos)) if(to != back) dfs2(dfs2,to,pos);
                if(s.at(pos) == '1') n++;
                else n--;
            };  
            auto dfs3 = [&](auto dfs3,int pos,int back) -> void {
                if(s.at(pos) == '1') n++;
                else n--;
                Z.update(n,1);
                for(auto to : Graph.at(pos)) if(to != back) dfs3(dfs3,to,pos);
                if(s.at(pos) == '1') n--;
                else n++;
            };
            for(auto to : Graph.at(pos)){
                if(to == back || to == big) continue;
                dfs2(dfs2,to,pos);
                if(s.at(pos) == '1') n++;
                else n--;
                dfs3(dfs3,to,pos);
                if(s.at(pos) == '1') n--;
                else n++;
            }
            return n;
        }
    };
    dfs(dfs,0,-1);
    cout << answer << endl;
}