#include <cassert>
#include <utility>
#include <vector>


// Centroid Decomposition
// Verification: Codeforces #190 Div.1 C https://codeforces.com/contest/321/submission/59093583
// find_current_centroids(int r): Enumerate centroid(s) of the subtree which `r` belongs to.
struct CentroidDecomposition {
    int V;
    std::vector<std::vector<int>> to;

private:
    std::vector<int> is_alive;
    std::vector<int> subtree_size;

    void decompose(int r, int conn_size, auto callback) {

        const int c = find_current_centroids(r, conn_size).first;
        is_alive.at(c) = 0;

        callback(c);

        for (int nxt : to.at(c)) {
            if (!is_alive.at(nxt)) continue;
            int next_size = subtree_size.at(nxt);
            if (subtree_size.at(nxt) > subtree_size.at(c)) next_size = subtree_size.at(r) - subtree_size.at(c);
            decompose(nxt, next_size, callback);
        }
    }

public:
    CentroidDecomposition(int v = 0) : V(v), to(v), is_alive(v, 1), subtree_size(v) {}

    CentroidDecomposition(int v, const std::vector<std::pair<int, int>> &tree_edges) : CentroidDecomposition(v) {
        for (auto e : tree_edges) add_edge(e.first, e.second);
    }

    void add_edge(int v1, int v2) {
        assert(0 <= v1 and v1 < V and 0 <= v2 and v2 < V);
        assert(v1 != v2);
        to.at(v1).push_back(v2), to.at(v2).emplace_back(v1);
    }

    std::pair<int, int> find_current_centroids(int r, int conn_size) {
        assert(is_alive.at(r));

        const int thres = conn_size / 2;

        int c1 = -1, c2 = -1;

        auto rec_search = [&](auto &&self, int now, int prv) -> void {
            bool is_centroid = true;
            subtree_size.at(now) = 1;
            for (int nxt : to.at(now)) {
                if (nxt == prv or !is_alive.at(nxt)) continue;
                self(self, nxt, now);
                subtree_size.at(now) += subtree_size.at(nxt);
                if (subtree_size.at(nxt) > thres) is_centroid = false;
            }
            if (conn_size - subtree_size.at(now) > thres) is_centroid = false;

            if (is_centroid) (c1 < 0 ? c1 : c2) = now;
        };
        rec_search(rec_search, r, -1);

        return {c1, c2};
    }

    void run(int r, auto callback) {
        int conn_size = 0;

        auto rec = [&](auto &&self, int now, int prv) -> void {
            ++conn_size;
            is_alive.at(now) = 1;

            for (int nxt : to.at(now)) {
                if (nxt == prv) continue;
                self(self, nxt, now);
            }
        };
        rec(rec, r, -1);

        decompose(r, conn_size, callback);
    }

    std::vector<int> centroid_decomposition(int r) {
        std::vector<int> res;
        run(r, [&](int v) { res.push_back(v); });
        return res;
    }
};


#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <chrono>
#include <cmath>
#include <complex>
#include <deque>
#include <forward_list>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iostream>
#include <limits>
#include <list>
#include <map>
#include <memory>
#include <numeric>
#include <optional>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <tuple>
#include <type_traits>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
using namespace std;
using lint = long long;
using pint = pair<int, int>;
using plint = pair<lint, lint>;
struct fast_ios { fast_ios(){ cin.tie(nullptr), ios::sync_with_stdio(false), cout << fixed << setprecision(20); }; } fast_ios_;
#define ALL(x) (x).begin(), (x).end()
#define FOR(i, begin, end) for(int i=(begin),i##_end_=(end);i<i##_end_;i++)
#define IFOR(i, begin, end) for(int i=(end)-1,i##_begin_=(begin);i>=i##_begin_;i--)
#define REP(i, n) FOR(i,0,n)
#define IREP(i, n) IFOR(i,0,n)
template <typename T> bool chmax(T &m, const T q) { return m < q ? (m = q, true) : false; }
template <typename T> bool chmin(T &m, const T q) { return m > q ? (m = q, true) : false; }
const std::vector<std::pair<int, int>> grid_dxs{{1, 0}, {-1, 0}, {0, 1}, {0, -1}};
int floor_lg(long long x) { return x <= 0 ? -1 : 63 - __builtin_clzll(x); }
template <class T1, class T2> T1 floor_div(T1 num, T2 den) { return (num > 0 ? num / den : -((-num + den - 1) / den)); }
template <class T1, class T2> std::pair<T1, T2> operator+(const std::pair<T1, T2> &l, const std::pair<T1, T2> &r) { return std::make_pair(l.first + r.first, l.second + r.second); }
template <class T1, class T2> std::pair<T1, T2> operator-(const std::pair<T1, T2> &l, const std::pair<T1, T2> &r) { return std::make_pair(l.first - r.first, l.second - r.second); }
template <class T> std::vector<T> sort_unique(std::vector<T> vec) { sort(vec.begin(), vec.end()), vec.erase(unique(vec.begin(), vec.end()), vec.end()); return vec; }
template <class T> int arglb(const std::vector<T> &v, const T &x) { return std::distance(v.begin(), std::lower_bound(v.begin(), v.end(), x)); }
template <class T> int argub(const std::vector<T> &v, const T &x) { return std::distance(v.begin(), std::upper_bound(v.begin(), v.end(), x)); }
template <class IStream, class T> IStream &operator>>(IStream &is, std::vector<T> &vec) { for (auto &v : vec) is >> v; return is; }

template <class OStream, class T> OStream &operator<<(OStream &os, const std::vector<T> &vec);
template <class OStream, class T, size_t sz> OStream &operator<<(OStream &os, const std::array<T, sz> &arr);
template <class OStream, class T, class TH> OStream &operator<<(OStream &os, const std::unordered_set<T, TH> &vec);
template <class OStream, class T, class U> OStream &operator<<(OStream &os, const pair<T, U> &pa);
template <class OStream, class T> OStream &operator<<(OStream &os, const std::deque<T> &vec);
template <class OStream, class T> OStream &operator<<(OStream &os, const std::set<T> &vec);
template <class OStream, class T> OStream &operator<<(OStream &os, const std::multiset<T> &vec);
template <class OStream, class T> OStream &operator<<(OStream &os, const std::unordered_multiset<T> &vec);
template <class OStream, class T, class U> OStream &operator<<(OStream &os, const std::pair<T, U> &pa);
template <class OStream, class TK, class TV> OStream &operator<<(OStream &os, const std::map<TK, TV> &mp);
template <class OStream, class TK, class TV, class TH> OStream &operator<<(OStream &os, const std::unordered_map<TK, TV, TH> &mp);
template <class OStream, class... T> OStream &operator<<(OStream &os, const std::tuple<T...> &tpl);

template <class OStream, class T> OStream &operator<<(OStream &os, const std::vector<T> &vec) { os << '['; for (auto v : vec) os << v << ','; os << ']'; return os; }
template <class OStream, class T, size_t sz> OStream &operator<<(OStream &os, const std::array<T, sz> &arr) { os << '['; for (auto v : arr) os << v << ','; os << ']'; return os; }
template <class... T> std::istream &operator>>(std::istream &is, std::tuple<T...> &tpl) { std::apply([&is](auto &&... args) { ((is >> args), ...);}, tpl); return is; }
template <class OStream, class... T> OStream &operator<<(OStream &os, const std::tuple<T...> &tpl) { os << '('; std::apply([&os](auto &&... args) { ((os << args << ','), ...);}, tpl); return os << ')'; }
template <class OStream, class T, class TH> OStream &operator<<(OStream &os, const std::unordered_set<T, TH> &vec) { os << '{'; for (auto v : vec) os << v << ','; os << '}'; return os; }
template <class OStream, class T> OStream &operator<<(OStream &os, const std::deque<T> &vec) { os << "deq["; for (auto v : vec) os << v << ','; os << ']'; return os; }
template <class OStream, class T> OStream &operator<<(OStream &os, const std::set<T> &vec) { os << '{'; for (auto v : vec) os << v << ','; os << '}'; return os; }
template <class OStream, class T> OStream &operator<<(OStream &os, const std::multiset<T> &vec) { os << '{'; for (auto v : vec) os << v << ','; os << '}'; return os; }
template <class OStream, class T> OStream &operator<<(OStream &os, const std::unordered_multiset<T> &vec) { os << '{'; for (auto v : vec) os << v << ','; os << '}'; return os; }
template <class OStream, class T, class U> OStream &operator<<(OStream &os, const std::pair<T, U> &pa) { return os << '(' << pa.first << ',' << pa.second << ')'; }
template <class OStream, class TK, class TV> OStream &operator<<(OStream &os, const std::map<TK, TV> &mp) { os << '{'; for (auto v : mp) os << v.first << "=>" << v.second << ','; os << '}'; return os; }
template <class OStream, class TK, class TV, class TH> OStream &operator<<(OStream &os, const std::unordered_map<TK, TV, TH> &mp) { os << '{'; for (auto v : mp) os << v.first << "=>" << v.second << ','; os << '}'; return os; }
#ifdef HITONANODE_LOCAL
const string COLOR_RESET = "\033[0m", BRIGHT_GREEN = "\033[1;32m", BRIGHT_RED = "\033[1;31m", BRIGHT_CYAN = "\033[1;36m", NORMAL_CROSSED = "\033[0;9;37m", RED_BACKGROUND = "\033[1;41m", NORMAL_FAINT = "\033[0;2m";
#define dbg(x) std::cerr << BRIGHT_CYAN << #x << COLOR_RESET << " = " << (x) << NORMAL_FAINT << " (L" << __LINE__ << ") " << __FILE__ << COLOR_RESET << std::endl
#define dbgif(cond, x) ((cond) ? std::cerr << BRIGHT_CYAN << #x << COLOR_RESET << " = " << (x) << NORMAL_FAINT << " (L" << __LINE__ << ") " << __FILE__ << COLOR_RESET << std::endl : std::cerr)
#else
#define dbg(x) ((void)0)
#define dbgif(cond, x) ((void)0)
#endif

#include <algorithm>
#include <vector>

// 0-indexed BIT (binary indexed tree / Fenwick tree) (i : [0, len))
template <class T> struct BIT {
    int n;
    std::vector<T> data;
    BIT(int len = 0) : n(len), data(len) {}
    void reset() { std::fill(data.begin(), data.end(), T(0)); }
    void add(int pos, T v) { // a[pos] += v
        pos++;
        while (pos > 0 and pos <= n) data[pos - 1] += v, pos += pos & -pos;
    }
    T sum(int k) const { // a[0] + ... + a[k - 1]
        T res = 0;
        while (k > 0) res += data[k - 1], k -= k & -k;
        return res;
    }

    T sum(int l, int r) const { return sum(r) - sum(l); } // a[l] + ... + a[r - 1]

    template <class OStream> friend OStream &operator<<(OStream &os, const BIT &bit) {
        T prv = 0;
        os << '[';
        for (int i = 1; i <= bit.n; i++) {
            T now = bit.sum(i);
            os << now - prv << ',', prv = now;
        }
        return os << ']';
    }
};


int main() {
    int N;
    cin >> N;

    CentroidDecomposition cd(N);

    for (int e = 0; e < N - 1; ++e) {
        int u, v;
        cin >> u >> v;
        --u, --v;
        cd.add_edge(u, v);
    }

    vector<int> V(N);

    {
        std::string S;
        cin >> S;
        for (int i = 0; i < N; ++i) {
            V.at(i) = (S.at(i) - '0') * 2 - 1;
        }
    }

    std::vector<int> is_alive(N, 1);

    lint ret = 0;

    std::vector<int> cnt(N * 2 + 1);
    BIT<int> bit(N * 2 + 1);

    for (int c : cd.centroid_decomposition(0)) {
        is_alive.at(c) = 0;

        int lo = 0, hi = 0;

        auto addbit = [&](int w) -> void {
            chmin(lo, w), chmax(hi, w);
            cnt.at(N + w)++;
            bit.add(N + w, 1);
        };

        addbit(V.at(c));
        if (V.at(c) > 0) ret++;

        for (int nxt : cd.to.at(c)) {
            if (!is_alive.at(nxt)) continue;

            std::vector<int> ws;

            auto dfs = [&](auto &&self, int now, int prv, int w) -> void {
                ws.push_back(w);
                // addbit(w);

                ret += bit.sum(-w + N + 1, N * 2 + 1);

                for (int nxt : cd.to.at(now)) {
                    if (nxt == prv or !is_alive.at(nxt)) continue;
                    self(self, nxt, now, w + V.at(nxt));
                }
            };
            dfs(dfs, nxt, c, V.at(nxt));

            for (int w : ws) {
                w += V.at(c);
                addbit(w);
            }
        }

        for (int i = lo; i <= hi; ++i) {
            int j = i + N;
            bit.add(j, -cnt.at(j));
            cnt.at(j) = 0;
        }
    }

    cout << ret << '\n';
}