#include <bits/stdc++.h>

using namespace std;

int v[100005];
long long dp[100005][3];
vector < vector <int> > G(100005);

void dfs(int nod){
    if(G[nod].size() == 0){
        dp[nod][0] = 0;
        dp[nod][1] = v[nod];
        dp[nod][2] = -v[nod];
        return;
    }
    long long s = 0;
    for(auto x : G[nod]){
        dfs(x);
        s += dp[x][0];
    }
    dp[nod][1] = s + v[nod];
    dp[nod][2] = s - v[nod];
    for(auto x : G[nod]){
        dp[nod][1] = max(dp[nod][1], s - dp[x][0] + dp[x][1]);
        dp[nod][2] = max(dp[nod][2], s - dp[x][0] + dp[x][2]);
    }
    dp[nod][0] = max(dp[nod][1] - v[nod], dp[nod][2] + v[nod]);
}

int main()
{
    int n,i,m,x,y;
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cin >> n;
    for(i = 1; i <= n; i++){
        cin >> v[i];
        dp[i][0] = dp[i][1] = dp[i][2] = -1e15;
    }
    for(i = 1; i < n; i++){
        cin >> x >> y;
        G[x].push_back(y);
    }
    dfs(1);
    cout << dp[1][0];
    return 0;
}