#include<bits/stdc++.h>

using namespace std;

int main(){
    cin.tie(0)->sync_with_stdio(false);
    int n; cin>>n;
    vector<int> a(n);
    for(int &x : a) cin>>x;
    vector<vector<int>> g(n);
    for(int e = 0; e+1<n; e++){
        int u, v;
        cin>>u>>v;
        u--, v--;
        g[u].push_back(v);
        g[v].push_back(u);
    }

    using pii = pair<int, int>;
    auto dfs = [&](auto &&self, int u, int p) -> pii {
        using T = tuple<int, int, int>;
        vector<T> child;
        for(int v : g[u]){
            if(v == p) continue;
            auto [par, imp] = self(self, v, u);
            child.emplace_back(imp - par, imp, par);
        }
        sort(child.rbegin(), child.rend());
        int par = 0, imp = !a[u];
        int cur = 0;
        for(auto [d, i, p] : child){
            cur += p; 
        }
        par = a[u] + cur;
        int cnt_imp = 0;
        // cout<<u+1<<":\n";
        // cout<<cur<<" -- "<<0<<"\n";
        for(auto [d, i, p] : child){
            cur += d; 
            cnt_imp++;
            //cout<<cur<<" -- "<<cnt_imp<<"\n";
            if(cnt_imp % 2){
                imp = max(imp, cur + !a[u]);
            } else {
                par = max(par, cur + a[u]);
            }
        }
        //cout<<u+1<<" "<<par<<" "<<imp<<"\n";
        return {par, imp};
    };
    auto [par, imp] = dfs(dfs, 0, 0);
    cout<<max(par, imp)<<"\n";
    return 0;
}