#include <bits/stdc++.h>
using namespace std;
long long modulo(long long base, long long exponent, long long modulus);
long long choose(long long n, long long k);
long long inverse(long long a, long long m);
void build();
long long ncr(long long n, long long r);
vector<long long> fact(1000010);
long long odd[1000010];
long long even[1000010];
long long sum(long long a, long long b) { return (a + b) % 1000000007; }
long long sub(long long a, long long b) {
  return (a - b + 1000000007) % 1000000007;
}
long long mult(long long a, long long b) { return (a * b) % 1000000007; }
long long ans;
vector<long long> a;
vector<long long> adj[1000010];
long long dist[1000010];
void dfs(long long x, long long p) {
  long long c = 0;
  for (int i = 0; i < adj[x].size(); i++) {
    long long y = adj[x][i];
    if (p == y) continue;
    dist[y] = dist[x] + 1;
    dfs(y, x);
    c++;
    if (c > 0) {
      ans = sum(ans, mult(mult(mult(odd[x], even[y]), a[x]), 2));
      ans = sum(ans, mult(mult(mult(even[x], odd[y]), -a[x]), 2));
    }
    odd[x] = sum(odd[x], even[y]);
    even[x] = sum(even[x], odd[y]);
  }
  odd[x] += 1;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long n;
  cin >> n;
  a.resize(n + 1);
  for (int i = 1; i <= n; i++) cin >> a[i];
  for (int i = 0; i < (n - 1); i++) {
    long long x, y;
    cin >> x >> y;
    adj[x].push_back(y);
    adj[y].push_back(x);
  }
  dfs(1, 0);
  for (int i = 1; i <= n; i++) {
    long long x = i;
    long long tod, teve;
    if (dist[i] % 2) {
      tod = even[1];
      teve = odd[1];
      ans =
          ((ans + 2 *
                      (odd[i] * (even[1] - odd[i] + 1) % 1000000007 -
                       even[i] * (odd[1] - even[i]) % 1000000007 + 1000000007) %
                      1000000007 * a[i] % 1000000007) %
               1000000007 +
           1000000007) %
          1000000007;
    } else {
      tod = odd[1];
      teve = even[1];
      ans = ((ans +
              2 *
                  (odd[i] * (odd[1] - odd[i] + 1) % 1000000007 -
                   even[i] * (even[1] - even[i]) % 1000000007 + 1000000007) %
                  1000000007 * a[i] % 1000000007) %
                 1000000007 +
             1000000007) %
            1000000007;
    }
    ans = sub(ans, a[x]);
  }
  cout << ans << endl;
  return 0;
}
long long ncr(long long n, long long r) {
  if (r > n || r < 0 || n < 0) return 0;
  long long ans = fact[n];
  long long temp = (fact[n - r] * fact[r]) % 1000000007;
  ans = (ans * inverse(temp, 1000000007)) % 1000000007;
  return ans;
}
void build() {
  fact[0] = 1;
  for (long long i = 1; i < 1000010; i++)
    fact[i] = (fact[i - 1] * i) % 1000000007;
}
long long modulo(long long base, long long exponent, long long modulus) {
  if (modulus == 1) return 0;
  long long result = 1;
  base = base % modulus;
  while (exponent > 0) {
    if (exponent % 2 == 1) {
      result = (result * base) % modulus;
    }
    exponent = exponent >> 1;
    base = (base * base) % modulus;
  }
  return result;
}
long long choose(long long n, long long k) {
  if (k == 0) return 1;
  return (n * choose(n - 1, k - 1)) / k;
}
void EE(long long a, long long b, long long &co1, long long &co2) {
  if (a % b == 0) {
    co1 = 0;
    co2 = 1;
    return;
  }
  EE(b, a % b, co1, co2);
  long long temp = co1;
  co1 = co2;
  co2 = temp - co2 * (a / b);
}
long long inverse(long long a, long long m) {
  long long x, y;
  EE(a, m, x, y);
  if (x < 0) x += m;
  return x;
}
