#include<iostream>
#include<vector>
#include<climits>
using namespace std;

int value[100001], n, tot, best;
vector<vector<int> > v;
bool visited[100001];
int sum[100001];

int dfs(int node)
{
    int ret = 0;
    visited[node] = true;
    int sz = (int)v[node].size();
    for (int i = 0; i < sz; i++)
    {
        int next = v[node][i];
        if (!visited[next])
            ret += dfs(next);
    }
    return sum[node] = value[node] + ret;
}

int main()
{
    best = INT_MAX;
    tot = 0;
    cin >> n;
    for (int i = 1; i <= n; i++)
    {
        cin >> value[i];
        tot += value[i];
    }
    v.resize(n + 1);
    for (int i = 0; i < n - 1; i++)
    {
        int a, b;
        cin >> a >> b;
        v[a].push_back(b);
        v[b].push_back(a);
    }
    dfs(1);
    for (int i = 1; i <= n; i++)
        if (abs(tot - sum[i] - sum[i]) < best)
            best = abs(tot - sum[i] - sum[i]);
    cout << best << endl;
    return 0;
}