#include <bits/stdc++.h>
long long gi() {
  long long x = 0, f = 1;
  char ch = getchar();
  while (!isdigit(ch)) f ^= ch == '-', ch = getchar();
  while (isdigit(ch)) x = x * 10 + ch - '0', ch = getchar();
  return f ? x : -x;
}
char S[200010];
int fir[200010], dis[400010], nxt[400010], id;
void link(int a, int b) { nxt[++id] = fir[a], fir[a] = id, dis[id] = b; }
int F[200010], cF[200010], G[200010], cG[200010];
void dfs(int x, int fa = -1) {
  G[x] = cG[x] = 1e9;
  for (int i = fir[x]; i; i = nxt[i]) {
    if (fa == dis[i]) continue;
    dfs(dis[i], x);
    if (F[dis[i]] >= F[x])
      cF[x] = F[x], F[x] = F[dis[i]] + 1;
    else
      cF[x] = std::max(cF[x], F[dis[i]] + 1);
    if (G[x] > G[dis[i]] + 1)
      cG[x] = G[x], G[x] = G[dis[i]] + 1;
    else
      cG[x] = std::min(cG[x], G[dis[i]] + 1);
  }
  if (S[x] == '1') {
    if (G[x] > F[x])
      cG[x] = G[x], G[x] = F[x];
    else
      cG[x] = std::min(cG[x], F[x]);
  }
}
long long ans;
void DFS(int x, int FF = 0, int GG = 1e9, int fa = -1) {
  int mx = FF, cm = 0;
  for (int i = fir[x]; i; i = nxt[i]) {
    if (fa == dis[i]) continue;
    if (F[dis[i]] + 1 > mx)
      cm = mx, mx = F[dis[i]] + 1;
    else
      cm = std::max(cm, F[dis[i]] + 1);
  }
  int _GG = GG;
  if (S[x] == '1') _GG = 0;
  ans += std::max(0, std::min(mx, cm + 2) - std::min(G[x], _GG));
  for (int i = fir[x], j = 0; i; i = nxt[i], ++j) {
    if (fa == dis[i]) {
      --j;
      continue;
    }
    int df = FF, dg = GG;
    if (F[x] != F[dis[i]] + 1)
      df = std::max(df, F[x]);
    else
      df = std::max(df, cF[x]);
    if (G[x] != G[dis[i]] + 1)
      dg = std::min(dg, G[x]);
    else
      dg = std::min(dg, cG[x]);
    DFS(dis[i], df + 1, dg + 1, x);
  }
}
int main() {
  int n = gi(), u, v;
  for (int i = 1; i < n; ++i) u = gi(), v = gi(), link(u, v), link(v, u);
  scanf("%s", S + 1);
  dfs(1);
  DFS(1);
  printf("%lld\n", ans + 1);
  return 0;
}
