#include <bits/stdc++.h>

using namespace std;
const int MAXN = 100100, INF = 0x3f3f3f3f;
vector<int> adj[MAXN];
int n, a[MAXN];

int dp[MAXN][2];
void solve(int v, int p = -1)
{
    int newdp[2] = {};
    dp[v][1] = -INF;
    bool isLeaf = true;

    for(int u : adj[v])
        if(u != p)
        {
            isLeaf = false;
            solve(u, v);

            newdp[0] = newdp[1] = -INF;
            for(int j = 0; j < 2; ++j)
                for(int k = 0; k < 2; ++k)
                {
                    newdp[(j + k) % 2] = max(newdp[(j + k) % 2], dp[v][j] + dp[u][k]);
                }

            dp[v][0] = newdp[0];
            dp[v][1] = newdp[1];
        }

    if(isLeaf)
    {
        dp[v][0] = 0;
        dp[v][1] = 0;
    }

    dp[v][!a[v]]++;
}

int main()
{
    #ifndef ONLINE_JUDGE
    freopen("input.txt","r",stdin);
    freopen("output.txt","w",stdout); 
    #endif
    ios_base::sync_with_stdio(false), cin.tie(NULL);
    cin >> n;
    for(int i = 1; i <= n; ++i)
        cin >> a[i];
    for(int i = 1, u, v; i < n; ++i)
    {
        cin >> u >> v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }

    solve(1);

    cout << max(dp[1][0], dp[1][1]) << endl;
}