#include <bits/stdc++.h>
using namespace std;
long long n, clr[300001][3] = {{0}};
vector<long long> v[300001];
void dfs(long long node, long long parent) {
  for (auto x : v[node]) {
    if (x == parent) continue;
    dfs(x, node);
    clr[node][1] += clr[x][1];
    clr[node][2] += clr[x][2];
  }
}
signed main() {
  cin.tie(0);
  cout.tie(0);
  ios_base::sync_with_stdio(false);
  cin >> n;
  long long r = 0, b = 0;
  for (long long i = 1; i < n + 1; i++) {
    long long c;
    cin >> c;
    if (c == 1) r++;
    if (c == 2) b++;
    clr[i][c]++;
  }
  for (long long i = 1; i < n; i++) {
    long long x, y;
    cin >> x >> y;
    v[x].push_back(y);
    v[y].push_back(x);
  }
  dfs(1, 1);
  long long ans = 0;
  if (b == 0 || r == 0) return cout << n - 1 << '\n', 0;
  for (long long i = 1; i < n + 1; i++) {
    if ((clr[i][2] == 0 && clr[i][1] == r) ||
        (clr[i][1] == 0 && clr[i][2] == b))
      ans++;
  }
  cout << ans;
}
