#include <bits/stdc++.h>

using ll = std::int64_t;

void point_update(
    int x, int i,
    std::vector<int> &diff,
    std::vector<std::map<int, int>> &diff_group,
    std::vector<int> &incr,
    int &count,
    const int B
){
    int ig = i / B;    
    if(diff[i] + incr[ig] == 1 && x == -1){
        count -= 1;
    }else if(diff[i] + incr[ig] == 0 && x == 1){
        count += 1;
    }

    diff_group[ig][diff[i]] -= 1;
    diff[i] += x;
    diff_group[ig][diff[i]] += 1;
}

void add(
    int x, int l, int r,
    std::vector<int> &diff,
    std::vector<std::map<int, int>> &diff_group,
    std::vector<int> &incr,
    int &count,
    const int B
){
    while(l < r && l % B > 0){
        point_update(x, l, diff, diff_group, incr, count, B);
        l += 1;
    }
    while(l < r && r % B > 0){
        point_update(x, r - 1, diff, diff_group, incr, count, B);
        r -= 1;
    }
    l /= B;
    r /= B;
    while(l < r){
        if(x == 1){
            count += diff_group[l][-incr[l]];
        }else{
            count -= diff_group[l][1 - incr[l]];
        }

        incr[l] += x;
        l += 1;
    }
}

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

    int N;
    std::cin >> N;

    std::vector<std::vector<int>> G(N + 1);
    for(int i=0;i<N-1;i++){
        int u, v;
        std::cin >> u >> v;

        G[u].emplace_back(v);
        G[v].emplace_back(u);
    }

    std::string S;
    std::cin >> S;

    std::vector<int> in(N + 1), out(N + 1), diff(N, 0);
    {
        int counter = 0;
        std::stack<std::tuple<int, int, int>> stack;
        stack.emplace(0, 1, -1);

        while(!stack.empty()){
            auto [t, v, p] = stack.top();
            stack.pop();

            if(t == 0){
                in[v] = counter;
                counter += 1;
                diff[in[v]] = S[v - 1] == '1' ? 1 : -1;
                if(p != -1){
                    diff[in[v]] += diff[in[p]];
                }
                stack.emplace(1, v, p);

                for(auto &w : G[v]){
                    if(w != p){
                        stack.emplace(0, w, v);
                    }
                }
            }else{
                out[v] = counter;
            }
        }
    }

    const int B = std::sqrt(N);
    int count = 0;
    std::vector<std::map<int, int>> diff_group((N + B - 1) / B);
    std::vector<int> incr((N + B - 1) / B, 0);
    for(int i=0;i<N;i++){
        diff_group[i / B][diff[i]] += 1;
        if(diff[i] >= 1){
            count += 1;
        }
    }

    ll res = 0;
    {
        std::stack<std::tuple<int, int, int>> stack;
        stack.emplace(0, 1, -1);

        while(!stack.empty()){
            auto [t, v, p] = stack.top();
            stack.pop();

            if(t == 0){
                stack.emplace(1, v, p);
                if(p != -1){
                    int xv = S[v - 1] == '1' ? 1 : -1;
                    int xp = S[p - 1] == '1' ? 1 : -1;
                    add(xv, 0, in[v], diff, diff_group, incr, count, B);
                    add(-xp, in[v], out[v], diff, diff_group, incr, count, B);
                    add(xv, out[v], diff.size(), diff, diff_group, incr, count, B);
                }

                res += count;
                
                for(auto &w : G[v]){
                    if(w != p){
                        stack.emplace(0, w, v);
                    }
                }
            }else{
                if(p != -1){
                    int xv = S[v - 1] == '1' ? 1 : -1;
                    int xp = S[p - 1] == '1' ? 1 : -1;
                    add(-xv, 0, in[v], diff, diff_group, incr, count, B);
                    add(xp, in[v], out[v], diff, diff_group, incr, count, B);
                    add(-xv, out[v], diff.size(), diff, diff_group, incr, count, B);
                }
            }
        }
    }

    int n = std::count(S.begin(), S.end(), '1');
    res -= n;
    res = res / 2 + n;
    std::cout << res << std::endl;
}