#[allow(unused_imports)]
use std::cmp::*;
#[allow(unused_imports)]
use std::collections::*;
use std::io::{Write, BufWriter};
// https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8
macro_rules! input {
    ($($r:tt)*) => {
        let stdin = std::io::stdin();
        let mut bytes = std::io::Read::bytes(std::io::BufReader::new(stdin.lock()));
        let mut next = move || -> String{
            bytes.by_ref().map(|r|r.unwrap() as char)
                .skip_while(|c|c.is_whitespace())
                .take_while(|c|!c.is_whitespace())
                .collect()
        };
        input_inner!{next, $($r)*}
    };
}

macro_rules! input_inner {
    ($next:expr) => {};
    ($next:expr,) => {};
    ($next:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($next, $t);
        input_inner!{$next $($r)*}
    };
}

macro_rules! read_value {
    ($next:expr, ( $($t:tt),* )) => { ($(read_value!($next, $t)),*) };
    ($next:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($next, $t)).collect::<Vec<_>>()
    };
    ($next:expr, chars) => {
        read_value!($next, String).chars().collect::<Vec<char>>()
    };
    ($next:expr, usize1) => (read_value!($next, usize) - 1);
    ($next:expr, $t:ty) => ($next().parse::<$t>().expect("Parse error"));
}

trait Bisect<T> {
    fn lower_bound(&self, val: &T) -> usize;
    fn upper_bound(&self, val: &T) -> usize;
}

impl<T: Ord> Bisect<T> for [T] {
    fn lower_bound(&self, val: &T) -> usize {
        let mut pass = self.len() + 1;
        let mut fail = 0;
        while pass - fail > 1 {
            let mid = (pass + fail) / 2;
            if &self[mid - 1] >= val {
                pass = mid;
            } else {
                fail = mid;
            }
        }
        pass - 1
    }
    fn upper_bound(&self, val: &T) -> usize {
        let mut pass = self.len() + 1;
        let mut fail = 0;
        while pass - fail > 1 {
            let mid = (pass + fail) / 2;
            if &self[mid - 1] > val {
                pass = mid;
            } else {
                fail = mid;
            }
        }
        pass - 1
    }
}

// Returns (root, children)
// This functions uses O(n) stack space.
// Complexity: O(n log n)-time, O(n)-space
// Verified by: ABC291-Ex (https://atcoder.jp/contests/abc291/submissions/39303290)
fn centroid_decompose(g: &[Vec<usize>]) -> (usize, Vec<Vec<usize>>) {
    fn find_subtree_sizes(g: &[Vec<usize>], v: usize, par: usize,
                          dp: &mut [usize], vis: &[bool]) {
        let mut sum = 1;
        for &w in &g[v] {
            if par == w || vis[w] { continue; }
            find_subtree_sizes(g, w, v, dp, vis);
            sum += dp[w];
        }
        dp[v] = sum;
    }
    fn centroid_decompose_inner(g: &[Vec<usize>], v: usize, par: usize,
                                ch: &mut [Vec<usize>],
                                dp: &mut [usize], vis: &mut [bool]) -> usize {
        let n = g.len();
        find_subtree_sizes(g, v, n, dp, vis);
        let cent = {
            let sz = dp[v];
            let find_centroid = |mut v: usize, mut par: usize| {
                loop {
                    let mut has_majority = false;
                    for &w in &g[v] {
                        if par == w || vis[w] { continue; }
                        if dp[w] > sz / 2 {
                            par = v;
                            v = w;
                            has_majority = true;
                            break;
                        }
                    }
                    if !has_majority {
                        return v;
                    }
                }
            };
            find_centroid(v, n)
        };
        if par < n {
            ch[par].push(cent);
        }
        // v was selected as a centroid
        // and will be ignored in the following decomposition procedure
        vis[cent] = true;
        for &w in &g[cent] {
            if !vis[w] {
                centroid_decompose_inner(g, w, cent, ch, dp, vis);
            }
        }
        cent
    }
    let n = g.len();
    let mut ch = vec![vec![]; n];
    // This Vec is used across multiple calls to `centroid_decompose_inner`
    let mut dp = vec![0; n];
    let mut vis = vec![false; n];
    let root = centroid_decompose_inner(&g, 0, n, &mut ch, &mut dp, &mut vis);
    (root, ch)
}

fn main() {
    // In order to avoid potential stack overflow, spawn a new thread.
    let stack_size = 104_857_600; // 100 MB
    let thd = std::thread::Builder::new().stack_size(stack_size);
    thd.spawn(|| solve()).unwrap().join().unwrap();
}

fn dfs(v: usize, par: usize, g: &[Vec<usize>], s: &[char], vis: &[bool], cur: i32, agg: &mut Vec<i32>) {
    let cur = if s[v] == '1' { cur + 1 } else { cur - 1 };
    agg.push(cur);
    for &w in &g[v] {
        if par == w || vis[w] { continue; }
        dfs(w, v, g, s, vis, cur, agg);
    }
}

fn calc_comb(init: i32, mut comb: Vec<i32>) -> i64 {
    comb.sort_unstable();
    let mut ret = 0;
    for &v in &comb {
        let idx = comb.lower_bound(&(-init - v + 1));
        ret += (comb.len() - idx) as i64;
    }
    ret
}

// https://yukicoder.me/problems/no/2892 (4)
fn solve() {
    input! {
        n: usize,
        uv: [(usize1, usize1); n - 1],
        s: chars,
    }
    let mut g = vec![vec![]; n];
    for &(u, v) in &uv {
        g[u].push(v);
        g[v].push(u);
    }
    let (root, ch) = centroid_decompose(&g);
    let mut vis = vec![false; n];
    let mut que = vec![root];
    let mut tot = 0;
    while let Some(v) = que.pop() {
        vis[v] = true;
        for &w in &ch[v] {
            que.push(w);
        }
        // search
        let mut agg = vec![];
        let init = if s[v] == '1' { 1 } else { -1 };
        for &c in &ch[v] {
            let mut me = vec![];
            dfs(c, v, &g, &s, &vis, 0, &mut me);
            agg.extend_from_slice(&me);
            tot -= calc_comb(init, me);
        }
        for &a in &agg {
            if init + a > 0 {
                tot += 2;
            }
        }
        tot += calc_comb(init, agg);
        if init == 1 {
            tot += 2;
        }
    }
    println!("{}", tot / 2);
}