#include <bits/stdc++.h>
using namespace std;
namespace fastIO1 {
inline char read() {
  static const int IN_LEN = 1000000;
  static char buf[IN_LEN], *s, *t;
  return (s == t               ? t = (s = buf) + fread(buf, 1, IN_LEN, stdin),
          (s == t ? -1 : *s++) : *s++);
}
template <class T>
inline void read(T &x) {
  static bool iosig;
  static char c;
  for (iosig = false, c = read(); !isdigit(c); c = read()) {
    if (c == '-') iosig = true;
    if (c == -1) return;
  }
  for (x = 0; isdigit(c); c = read()) x = ((x + (x << 2)) << 1) + (c ^ '0');
  if (iosig) x = -x;
}
inline char readc(char &c) {
  for (c = read(); !isalpha(c) && !isdigit(c); c = read())
    if (c == -1) return 0;
}
const int OUT_LEN = 10000000;
char obuf[OUT_LEN], *ooh = obuf;
inline void print(char c) {
  if (ooh == obuf + OUT_LEN) fwrite(obuf, 1, OUT_LEN, stdout), ooh = obuf;
  *ooh++ = c;
}
template <class T>
inline void print(T x) {
  static int buf[30], cnt;
  if (x == 0)
    print('0');
  else {
    if (x < 0) print('-'), x = -x;
    for (cnt = 0; x; x /= 10) buf[++cnt] = x % 10 + 48;
    while (cnt) print((char)buf[cnt--]);
  }
}
inline void flush() { fwrite(obuf, 1, ooh - obuf, stdout); }
}  // namespace fastIO1
namespace fastIO2 {
template <class T>
inline void read(T &x) {
  static bool iosig;
  static char c;
  for (iosig = false, c = getchar(); !isdigit(c); c = getchar()) {
    if (c == '-') iosig = true;
    if (c == -1) return;
  }
  for (x = 0; isdigit(c); c = getchar()) x = ((x + (x << 2)) << 1) + (c ^ '0');
  if (iosig) x = -x;
}
}  // namespace fastIO2
using namespace fastIO1;
int n, E, fi[(200010)], ne[((200010) << 1)], b[((200010) << 1)];
char str[(200010)];
int f[(200010)], sf[(200010)], siz[(200010)], mn[(200010)];
long long ans;
void add(int x, int y) { ne[++E] = fi[x], fi[x] = E, b[E] = y; }
void dfs1(int u, int pre) {
  if (str[u] == '1')
    mn[u] = 0, siz[u] = 1;
  else
    mn[u] = (0x7f7f7f7f);
  for (int i = fi[u]; i; i = ne[i]) {
    int v = b[i];
    if (v == pre) continue;
    dfs1(v, u), siz[u] += siz[v];
    if (f[v] + 1 > f[u])
      sf[u] = f[u], f[u] = f[v] + 1;
    else
      sf[u] = max(sf[u], f[v] + 1);
    if (siz[u]) mn[u] = min(mn[u], f[v] + 1);
  }
}
void dfs2(int u, int pre) {
  int tmp = min(f[u] - 1, sf[u] + 1);
  if (tmp >= mn[u]) ans += 0ll + tmp - mn[u] + 1;
  for (int i = fi[u]; i; i = ne[i]) {
    int v = b[i];
    if (v == pre) continue;
    int len = f[u] == f[v] + 1 ? sf[u] + 1 : f[u] + 1;
    if (f[v] < len)
      sf[v] = f[v], f[v] = len;
    else
      sf[v] = max(sf[v], len);
    if (siz[v] < siz[1]) mn[v] = min(mn[v], len);
    dfs2(v, u);
  }
}
int main() {
  read(n);
  for (int i = 1; i < n; i++) {
    int x, y;
    read(x), read(y);
    add(x, y), add(y, x);
  }
  for (int i = 1; i <= n; i++) readc(str[i]);
  dfs1(1, 0), dfs2(1, 0);
  cout << ans + 1;
}
