#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<int, int>
#define pll pair<ll, ll>
#define vi vector<int>
#define vl vector<ll>
#define ov4(a, b, c, d, name, ...) name
#define rep3(i, a, b, c) for(ll i = (a); i < (b); i += (c))
#define rep2(i, a, b) rep3(i, a, b, 1)
#define rep1(i, n) rep2(i, 0, n)
#define rep0(n) rep1(aaaaa, n)
#define rep(...) ov4(__VA_ARGS__, rep3, rep2, rep1, rep0)(__VA_ARGS__)
#define per(i, a, b) for(ll i = (a) - 1; i >= (b); i--)
#define fore(e, v) for(auto &&e : v)
#define all(a) begin(a), end(a)
#define si(a) (int)(size(a))
#define lb(v, x) (lower_bound(all(v), x) - begin(v))
#define eb emplace_back

template <typename T, typename S> bool chmin(T &a, const S &b) { return a > b ? a = b, 1 : 0; }
template <typename T, typename S> bool chmax(T &a, const S &b) { return a < b ? a = b, 1 : 0; }

const int INF = 1e9 + 100;
const ll INFL = 3e18 + 100;

#define i128 __int128_t

struct _ {
    _() { cin.tie(0)->sync_with_stdio(0), cout.tie(0); }
} __;

struct BIT {
    vi a;
    BIT(int n) : a(n + 1) {}
    void add(int i, int x) {
        i++;
        while(i < si(a)) a[i] += x, i += i & -i;
    }
    int sum(int r) {
        int s = 0;
        while(r) s += a[r], r -= r & -r;
        return s;
    }
    int sum(int l, int r) { return sum(r) - sum(l); }
};

int main() {
    int n;
    cin >> n;
    vector<vi> g(n);
    rep(n - 1) {
        int x, y;
        cin >> x >> y;
        --x, --y;
        g[x].eb(y), g[y].eb(x);
    }

    string s;
    cin >> s;
    vi a(n);
    rep(i, n) a[i] = (s[i] == '1' ? 1 : -1);

    if(n == 1) {
        cout << count(all(a), 1) << endl;
        exit(0);
    }

    vi sub(n), v(n);
    auto dfs = [&](auto &&f, int x, int p) -> void {
        v[x] += a[x];
        sub[x]++;
        if(g[x][0] == p) swap(g[x][0], g[x].back());
        fore(e, g[x]) {
            if(e == p) continue;
            v[e] = v[x];
            f(f, e, x);
            sub[x] += sub[e];
            if(sub[e] > sub[g[x][0]]) swap(e, g[x][0]);
        }
        return;
    };
    dfs(dfs, 0, -1);

    vi in(n), out(n), tour(n);
    int idx = 0;
    {
        auto dfs = [&](auto &&f, int x, int p) -> void {
            tour[idx] = x;
            in[x] = idx++;
            out[x] = in[x] + sub[x];
            fore(e, g[x]) if(e != p) f(f, e, x);
        };
        dfs(dfs, 0, -1);
    }

    ll ans = count(all(a), 1);
    BIT bit(n * 2 + 1);

    int car = n;

    vi tmp;
    // rep(i, n) cout << v[i] << " ";
    // cout << endl;

    auto add = [&](int i) {
        bit.add(i + car, 1);
        tmp.eb(i + car);
    };
    auto dfs2 = [&](auto &&f, int x, int p, bool clear) -> void {
        rep(i, 1, si(g[x])) {
            int e = g[x][i];
            if(e == p) continue;
            f(f, e, x, true);
        }
        if(g[x][0] != p) f(f, g[x][0], x, false);

        ll tans = 0;
        tans += bit.sum(v[x] - a[x] + car + 1, 2 * n + 1);
        add(v[x]);
        rep(i, 1, si(g[x])) {
            int e = g[x][i];
            if(e == p) continue;
            rep(j, in[e], out[e]) {
                int t = tour[j];
                int tar = 2 * v[x] - a[x] - v[t];
                tans += bit.sum(tar + car + 1, 2 * n + 1);
            }
            rep(j, in[e], out[e]) add(v[tour[j]]);
        }
        // cout << x << ": " << tans << endl;

        ans += tans;
        if(clear) {
            fore(i, tmp) bit.add(i, -1);
            tmp.clear();
        }
    };
    dfs2(dfs2, 0, -1, true);
    cout << ans << endl;
}