#include <bits/stdc++.h>
using namespace std;
long long power(long long a, long long b) {
  long long ans = 1;
  while (b > 0) {
    if (b % 2 != 0) {
      ans = (ans * a) % 1000000007;
    }
    a = ((a % 1000000007) * (a % 1000000007)) % 1000000007;
    b >>= 1;
  }
  return ans;
}
void sieve(int n) {
  bool prime[n + 1];
  memset(prime, true, sizeof(prime));
  for (int p = 2; p * p <= n; p++) {
    if (prime[p]) {
      for (int i = p * p; i <= n; i += p) prime[i] = false;
    }
  }
  for (int p = 2; p <= n; p++) {
    if (prime[p]) cout << p << " ";
  }
}
pair<int, int> dfs(int i, bool vis[], int col[], vector<int> adj[], int cnt[],
                   int &ans) {
  vis[i] = true;
  int p = 0, q = 0;
  for (auto j : adj[i]) {
    if (vis[j]) continue;
    pair<int, int> ha;
    ha = dfs(j, vis, col, adj, cnt, ans);
    p += ha.first;
    q += ha.second;
  }
  if (col[i] == 1) p++;
  if (col[i] == 2) q++;
  if ((cnt[1] - p == 0 && q == 0) || (cnt[2] - q == 0 && p == 0)) {
    ans++;
  }
  return {p, q};
}
int main() {
  std::ios::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  ;
  int t = 1;
  while (t--) {
    int n;
    cin >> n;
    int a[n + 1];
    int cnt[3];
    cnt[1] = 0;
    cnt[2] = 0;
    cnt[0] = 0;
    for (int i = 1; i <= n; i++) {
      cin >> a[i];
      cnt[a[i]]++;
    }
    if (n == 2) {
      cout << 1;
      return 0;
    }
    vector<int> adj[n + 1];
    int root;
    for (int i = 0; i < n - 1; i++) {
      int p, q;
      cin >> p >> q;
      adj[p].push_back(q);
      adj[q].push_back(p);
      if (adj[p].size() > 1) root = p;
      if (adj[q].size() > 1) root = q;
    }
    bool vis[n + 1];
    memset(vis, false, sizeof(vis));
    int ans = 0;
    ;
    pair<int, int> yo;
    yo = dfs(root, vis, a, adj, cnt, ans);
    cout << ans;
  }
  return 0;
}
