#include <bits/stdc++.h>
const int MAXN = 200010;
int head[MAXN], nxt[MAXN << 1], to[MAXN << 1], tot;
void addedge(int b, int e) {
  nxt[++tot] = head[b];
  to[head[b] = tot] = e;
  nxt[++tot] = head[e];
  to[head[e] = tot] = b;
}
int n;
char buf[MAXN];
bool hav[MAXN];
int L[MAXN];
struct node {
  int fir, sec;
  void ins(int x) {
    if (x >= fir)
      sec = fir, fir = x;
    else
      sec = std::max(sec, x);
  }
} val[MAXN];
void dfs1(int u, int fa = 0) {
  hav[u] = buf[u] == '1';
  L[u] = hav[u] ? 0 : std::numeric_limits<int>::max();
  for (int i = head[u]; i; i = nxt[i])
    if (to[i] != fa) {
      dfs1(to[i], u);
      hav[u] += hav[to[i]];
      val[u].ins(val[to[i]].fir + 1);
      if (hav[to[i]]) L[u] = std::min(L[u], val[to[i]].fir + 1);
    }
}
long long ans = 1;
void dfs2(int u, int fa = 0, int ma = -1) {
  node tv = val[u];
  tv.ins(ma);
  int l = L[u];
  if (hav[1] - hav[u]) l = std::min(l, ma);
  int r = std::min(tv.fir - 1, tv.sec + 1);
  if (l <= r) ans += r - l + 1;
  for (int i = head[u]; i; i = nxt[i])
    if (to[i] != fa)
      dfs2(to[i], u, (val[to[i]].fir + 1 == tv.fir ? tv.sec : tv.fir) + 1);
}
int main() {
  std::ios_base::sync_with_stdio(false), std::cin.tie(0);
  std::cin >> n;
  for (int i = 1, t1, t2; i < n; ++i) std::cin >> t1 >> t2, addedge(t1, t2);
  std::cin >> buf + 1;
  dfs1(1);
  dfs2(1);
  std::cout << ans << std::endl;
  return 0;
}
