#include 
using namespace std;
typedef long long ll;
const int maxn = 1e5 + 10;
int n;
int experience[maxn];
vector graph[maxn];
ll dp[maxn][3];

void dfs(int node, int parent) {
    ll sum = 0;
    for(int neighbour : graph[node]) {
        if(neighbour != parent) {
            dfs(neighbour, node);
            sum += dp[neighbour][0];
        }
    }
    dp[node][1] = sum + experience[node];
    dp[node][2] = sum - experience[node];
    
    for(int neighbour : graph[node]) {
        if(neighbour != parent) {
            dp[node][1] = max(dp[node][1], sum - dp[neighbour][0] + dp[neighbour][1]);
            dp[node][2] = max(dp[node][2], sum - dp[neighbour][0] + dp[neighbour][2]);
        }
    }
    dp[node][0] = max(dp[node][1] - experience[node], dp[node][2] + experience[node]);
}
int main()
{
    ios_base::sync_with_stdio(false);
    cin >> n;
    
    for(int i = 0; i < n; i++) {
        cin >> experience[i];
    }
    for(int i = 1; i < n; i++) {
        int a, b;
        cin >> a >> b;
        a--; b--;
    
        graph[a].push_back(b);
        graph[b].push_back(a);
    }
    dfs(0, -1);
    
    cout << dp[0][0] << endl;
    return 0;
}