#include <bits/stdc++.h>
using namespace std;
int n;
vector<int> tree[300003];
int colors[300003];
int blueC[300003];
int redC[300003];
int ans = 0;
pair<int, int> dfs(int nd, int pr) {
  int blue = (colors[nd] == 2);
  int red = (colors[nd] == 1);
  for (int i = 0; i < (int)tree[nd].size(); i++) {
    if (tree[nd][i] == pr) continue;
    pair<int, int> sub = dfs(tree[nd][i], nd);
    if ((bool)sub.first ^ (bool)sub.second) {
      if (sub.first)
        ans += (blueC[0] == sub.first);
      else
        ans += (redC[0] == sub.second);
    }
    blue += sub.first;
    red += sub.second;
  }
  return make_pair(blue, red);
}
void solve() {
  scanf("%d", &n);
  for (int i = 1; i <= n; i++) scanf("%d", &colors[i]);
  int u, v;
  for (int i = 1; i < n; i++) {
    scanf("%d %d", &u, &v);
    tree[u].push_back(v);
    tree[v].push_back(u);
  }
  memset(blueC, 0, sizeof(blueC));
  memset(redC, 0, sizeof(redC));
  for (int i = 1; i <= n; i++) {
    if (colors[i] == 1)
      redC[0]++;
    else if (colors[i] == 2)
      blueC[0]++;
  }
  dfs(1, 0);
  printf("%d", ans);
}
int main() { solve(); }
