#include <bits/stdc++.h>
using namespace std;
vector<vector<long long int>> graph(2003);
vector<long long int> visited(2003), dp(2003), visited1(2003);
long long int d, n;
vector<long long int> a(2003);
long long int ans = 0;
void dfs(long long int u, long long int val) {
  visited[u] = 1;
  dp[u] = 1;
  for (long long int i = 0; i < graph[u].size(); i++) {
    if (a[graph[u][i]] > val && a[graph[u][i]] <= val + d) {
      if (!visited[graph[u][i]]) {
        dfs(graph[u][i], val);
        dp[u] = (dp[u] * (dp[graph[u][i]] + 1)) % 1000000007;
      }
    } else if (a[graph[u][i]] == val && !visited1[graph[u][i]]) {
      if (!visited[graph[u][i]]) {
        dfs(graph[u][i], val);
        dp[u] = (dp[u] * (dp[graph[u][i]] + 1)) % 1000000007;
      }
    }
  }
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  cin >> d >> n;
  for (long long int i = 1; i <= n; i++) {
    cin >> a[i];
  }
  for (long long int i = 0; i < n - 1; i++) {
    long long int u, v;
    cin >> u >> v;
    graph[u].push_back(v);
    graph[v].push_back(u);
  }
  for (int i = 1; i <= n; i++) {
    visited1[i] = 1;
    fill(visited.begin(), visited.end(), 0);
    fill(dp.begin(), dp.end(), 0);
    dfs(i, a[i]);
    ans = (ans + dp[i]) % 1000000007;
  }
  cout << ans << "\n";
}
