#include <bits/stdc++.h>
using namespace std;
long long r;
vector<int> g[200005];
int n;
bool tk[200005];
int fat[200005];
int szt[200005];
long long v[200005];
int calcsz(int x, int f) {
  szt[x] = 1;
  for (auto y : g[x])
    if (y != f && !tk[y]) szt[x] += calcsz(y, x);
  return szt[x];
}
void dfs(int x, int f, int d, long long s, long long* a, int* q) {
  d ^= 1;
  if (d)
    s += v[x];
  else
    s -= v[x];
  a[d] += s;
  q[d]++;
  for (int y : g[x]) {
    if (tk[y] || y == f) continue;
    dfs(y, x, d, s, a, q);
  }
}
void cdfs(int x = 0, int f = -1, int sz = -1) {
  if (sz < 0) sz = calcsz(x, -1);
  for (auto y : g[x])
    if (!tk[y] && szt[y] * 2 >= sz) {
      szt[x] = 0;
      cdfs(y, f, sz);
      return;
    }
  tk[x] = 1;
  fat[x] = f;
  r += v[x];
  long long d[2] = {0, v[x]};
  int q[2] = {0, 1};
  for (int y : g[x]) {
    if (tk[y]) continue;
    long long d2[2] = {0, 0};
    int q2[2] = {0, 0};
    dfs(y, x, 0, 0, d2, q2);
    d2[0] %= 1000000007;
    d2[1] %= 1000000007;
    r += 2 * (q[0] * d2[1] + q2[1] * d[0]);
    r %= 1000000007;
    r += 2 * (q[1] * (1000000007 - d2[0]) + q2[0] * d[1]);
    r %= 1000000007;
    q[0] += q2[1];
    q[1] += q2[0];
    d[0] += (d2[1] - q2[1] * v[x] % 1000000007);
    d[0] %= 1000000007;
    d[1] += ((1000000007 - d2[0]) + q2[0] * v[x] % 1000000007);
    d[1] %= 1000000007;
  }
  for (auto y : g[x])
    if (!tk[y]) cdfs(y, x);
}
void centroid() {
  memset(tk, 0, sizeof(tk));
  cdfs();
}
int main() {
  scanf("%d", &n);
  for (int i = 0; i < (n); i++) scanf("%lld", v + i);
  for (int i = 1; i < (n); i++) {
    int x, y;
    scanf("%d%d", &x, &y);
    x--;
    y--;
    g[x].push_back(y);
    g[y].push_back(x);
  }
  centroid();
  r %= 1000000007;
  r += 1000000007;
  r %= 1000000007;
  printf("%lld\n", r);
  return 0;
}
