#include<bits/stdc++.h>
using namespace std;
#define int long long
#define ii pair <int, int>
#define app push_back
#define all(a) a.begin(), a.end()
#define bp __builtin_popcountll
#define ll long long
#define mp make_pair
#define f first
#define s second
#define Time (double)clock()/CLOCKS_PER_SEC
#define debug(x) std::cout << #x << ": " << x << '\n';
const int N = 1007;
vector <int> g[N];
int n, a[N];
vector <int> dp[N];
int ad[N];
void dfs(int u, int p) {
    for (int v : g[u]) {
        if (v != p) {
            dfs(v, u);
            for (auto e : dp[v])
                dp[u].app(e);
            ad[u] += ad[v];
        }   
    }   
    sort(all(dp[u]));
    reverse(all(dp[u]));
    int cur = a[u], f = -1;
    for (int i = 0; i < dp[u].size(); ++i) {
        if (i % 2 == 0 && cur >= dp[u][i]) {
            vector <int> su = {cur};
            for (int j = i; j < dp[u].size(); ++j)
                su.app(dp[u][j]);
            dp[u] = su;
            return;                                         
        }   
        cur += dp[u][i] * f;
        f = -f;
    }       
    if (dp[u].size() % 2 == 0) {
        dp[u] = {cur};
    }   
    else {
        dp[u].clear();
        ad[u] += cur;
    }   
}   
int get(int u) {
    int f = 1, ans = 0;
    dp[u].app(ad[u]);
    for (auto e : dp[u]) {
        ans += e * f;
        f = -f;
    }   
    return ans;
}   
signed main() {
    #ifdef HOME
    freopen("input.txt", "r", stdin);
    #else
    #define endl '\n'
    ios_base::sync_with_stdio(0); cin.tie(0);
    #endif
    cin >> n;
    for (int i = 1; i <= n; ++i)
        cin >> a[i];
    for (int i = 0; i < n - 1; ++i) {
        int u, v;
        cin >> u >> v;
        g[u].app(v); g[v].app(u);
    }   
    dfs(1, 1);
    cout << get(1) << endl;
}