#include <bits/stdc++.h>
template <class T>
bool MX(T &l, const T &r) {
  return l < r ? l = r, 1 : 0;
}
template <class T>
bool MN(T &l, const T &r) {
  return l > r ? l = r, 1 : 0;
}
using namespace std;
const long long MOD = 1e9 + 7;
vector<long long> a;
vector<vector<long long> > g;
long long ans = 0;
bool found = false;
void dfs(int par, int me, int col) {
  for (int ne : g[me]) {
    if (ne == par) continue;
    dfs(me, ne, col);
    if (a[ne] == col) {
      if (a[me] == (col % 2) + 1) {
        cout << 0 << endl;
        exit(0);
      } else
        a[me] = col;
    }
  }
}
void dfs2(int par, int me) {
  for (int ne : g[me]) {
    if (ne == par) continue;
    if (a[ne] == 2) {
      ++ans;
      found = true;
      break;
    }
    dfs2(me, ne);
    if (found) {
      if (a[ne] != 1) ++ans;
      break;
    }
  }
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  long long n, r, b, u, v;
  cin >> n;
  a.resize(n);
  g.resize(n);
  for (int i = 0; i < (int)n; ++i) {
    cin >> a[i];
    if (a[i] == 1)
      r = i;
    else if (a[i] == 2)
      b = i;
  }
  for (int i = 0; i < (int)n - 1; ++i) {
    cin >> u >> v;
    g[--u].push_back(--v);
    g[v].push_back(u);
  }
  dfs(-1, r, 1);
  dfs(-1, b, 2);
  dfs2(-1, r);
  cout << ans << endl;
  return 0;
}
