#include <bits/stdc++.h>

using ll = std::int64_t;

void dfs(
    int v,
    int p,
    int &counter,
    std::vector<int> &in,
    std::vector<int> &out,
    std::vector<int> &diff,
    const std::vector<std::vector<int>> &G,
    const std::string &S
){
    in[v] = counter;
    counter += 1;
    diff[in[v]] = S[v - 1] == '1' ? 1 : -1;
    if(p != -1){
        diff[in[v]] += diff[in[p]];
    }

    for(auto &w : G[v]){
        if(w != p){
            dfs(w, v, counter, in, out, diff, G, S);
        }
    }

    out[v] = counter;
}

ll search(
    int x, int l, int r,
    const std::vector<int> &diff,
    const std::vector<int> &diff_group,
    const std::vector<int> &incr,
    const int B
){
    ll res = 0;
    while(l < r && l % B > 0){
        if(diff[l] + incr[l / B] >= x){
            res += 1;
        }
        l += 1;
    }
    while(l < r && r % B > 0){
        if(diff[r - 1] + incr[(r - 1) / B] >= x){
            res += 1;
        }
        r -= 1;
    }
    while(l < r){
        int last = std::min<int>(l + B, diff_group.size());
        res +=
            diff_group.begin() + last
            - std::lower_bound(diff_group.begin() + l, diff_group.begin() + last, x - incr[l / B]);
        l = last;
    }

    return res;
}

void add(
    int x, int l, int r,
    std::vector<int> &diff,
    std::vector<int> &diff_group,
    std::vector<int> &incr,
    const int B
){
    auto update_point = [&](int i){
        int first = i / B * B, last = std::min<int>(first + B, diff_group.size());
        if(x == -1){
            int j =
                std::lower_bound(diff_group.begin() + first, diff_group.begin() + last, diff[i])
                - diff_group.begin();
            diff_group[j] += x;
        }else{
            int j =
                std::upper_bound(diff_group.begin() + first, diff_group.begin() + last, diff[i])
                - diff_group.begin();
            j -= 1;
            diff_group[j] += x;
        }
        diff[i] += x;
    };

    while(l < r && l % B > 0){
        update_point(l);
        l += 1;
    }
    while(l < r && r % B > 0){
        update_point(r - 1);
        r -= 1;
    }
    l /= B;
    r /= B;
    while(l < r){
        incr[l] += x;
        l += 1;
    }
}

ll dfs2(
    int v,
    int p,
    const std::vector<int> &in,
    const std::vector<int> &out,
    std::vector<int> &diff,
    std::vector<int> &diff_group,
    std::vector<int> &incr,
    const std::vector<std::vector<int>> &G,
    const std::string &S,
    const int B
){
    ll res = 0;
    res += search(1, 0, diff.size(), diff, diff_group, incr, B);

    int xv = S[v - 1] == '1' ? 1 : -1;
    for(auto &w : G[v]){
        if(w != p){
            int xw = S[w - 1] == '1' ? 1 : -1;
            add(xw, 0, in[w], diff, diff_group, incr, B);
            add(-xv, in[w], out[w], diff, diff_group, incr, B);
            add(xw, out[w], diff.size(), diff, diff_group, incr, B);
            res += dfs2(w, v, in, out, diff, diff_group, incr, G, S, B);
            add(-xw, 0, in[w], diff, diff_group, incr, B);
            add(xv, in[w], out[w], diff, diff_group, incr, B);
            add(-xw, out[w], diff.size(), diff, diff_group, incr, B);
        }
    }

    return res;
}

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;
        dfs(1, -1, counter, in, out, diff, G, S);
    }

    const int B = std::sqrt(N);
    std::vector<int> diff_group(diff), incr((N + B - 1) / B, 0);
    for(int i=0;i<N;i+=B){
        std::sort(diff_group.begin() + i, diff_group.begin() + std::min(i + B, N));
    }

    ll res = dfs2(1, -1, in, out, diff, diff_group, incr, G, S, B);
    int n = std::count(S.begin(), S.end(), '1');
    res -= n;
    res = res / 2 + n;
    std::cout << res << std::endl;
}