#include <bits/stdc++.h>
using namespace std;
long long gcd(long long a, long long b) {
  if (b > a) {
    return gcd(b, a);
  }
  if (b == 0) {
    return a;
  }
  return gcd(b, a % b);
}
long long expo(long long a, long long b, long long mod) {
  long long res = 1;
  while (b > 0) {
    if (b & 1) res = (res * a) % mod;
    a = (a * a) % mod;
    b = b >> 1;
  }
  return res;
}
vector<int> sieve(int n) {
  int *arr = new int[n + 1]();
  vector<int> vect;
  for (int i = 2; i <= n; i++)
    if (arr[i] == 0) {
      vect.push_back(i);
      for (int j = 2 * i; j <= n; j += i) arr[j] = 1;
    }
  return vect;
}
void extendgcd(long long a, long long b, long long *v) {
  if (b == 0) {
    v[0] = 1;
    v[1] = 0;
    v[2] = a;
    return;
  }
  extendgcd(b, a % b, v);
  long long x = v[1];
  v[1] = v[0] - v[1] * (a / b);
  v[0] = x;
  return;
}
long long mminv(long long a, long long b) {
  long long arr[3];
  extendgcd(a, b, arr);
  return arr[0];
}
long long mminvprime(long long a, long long b) { return expo(a, b - 2, b); }
bool revsort(long long a, long long b) { return a > b; }
void swap(int &x, int &y) {
  int temp = x;
  x = y;
  y = temp;
}
long long combination(long long n, long long r, long long m, long long *fact) {
  long long val1 = fact[n];
  long long val2 = mminvprime(fact[r], m);
  long long val3 = mminvprime(fact[n - r], m);
  return ((val1 * val2) % m * val3) % m;
}
void dfs(int start, vector<int> *edges, bool *visited, int *blues, int *reds,
         int *color, vector<pair<int, int>> &childs) {
  if (color[start] == 1) blues[start]++;
  if (color[start] == 2) reds[start]++;
  visited[start] = true;
  for (int i = 0; i < edges[start].size(); i++) {
    if (visited[edges[start][i]]) continue;
    dfs(edges[start][i], edges, visited, blues, reds, color, childs);
    blues[start] += blues[edges[start][i]];
    reds[start] += reds[edges[start][i]];
    childs.push_back({start, edges[start][i]});
  }
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int n;
  cin >> n;
  int color[n];
  int sum1 = 0;
  int sum2 = 0;
  for (int i = 0; i < n; i++) {
    cin >> color[i];
    if (color[i] == 1) sum1++;
    if (color[i] == 2) sum2++;
  }
  vector<int> *edges = new vector<int>[n];
  vector<int> *ans1 = new vector<int>[n];
  for (int i = 0; i < n - 1; i++) {
    int u, v;
    cin >> u >> v;
    u--;
    v--;
    edges[u].push_back(v);
    edges[v].push_back(u);
    ans1[u].push_back(1);
    ans1[v].push_back(1);
  }
  int *blues = new int[n]();
  int *reds = new int[n]();
  bool *visited = new bool[n]();
  vector<pair<int, int>> childs;
  dfs(0, edges, visited, blues, reds, color, childs);
  int ans = 0;
  set<pair<int, int>> s;
  for (int i = 0; i < childs.size(); i++) {
    int x = childs[i].second;
    int blue = blues[x];
    int red = reds[x];
    if (blue == 0 && red == sum2) ans++;
    if (red == 0 && blue == sum1) ans++;
  }
  cout << ans << endl;
  return 0;
}
