#include "bits/stdc++.h"
using namespace std;
#define all(x) begin(x),end(x)
template<typename A, typename B> ostream& operator<<(ostream &os, const pair<A, B> &p) { return os << '(' << p.first << ", " << p.second << ')'; }
template<typename T_container, typename T = typename enable_if<!is_same<T_container, string>::value, typename T_container::value_type>::type> ostream& operator<<(ostream &os, const T_container &v) { string sep; for (const T &x : v) os << sep << x, sep = " "; return os; }
#define debug(a) cerr << "(" << #a << ": " << a << ")\n";
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int,int> pi;
const int mxN = 1e5+1, oo = 1e9;
int main() {
    int n; cin >> n;
    vi a(n);
    for(auto& i : a) cin >> i;
    vvi adj(n);
    for(int i=1;i<n;++i) {
        int u,v; cin >> u >> v;
        --u,--v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }
    auto dfs = [&](auto&& self, int at, int from) -> array<int,2> {
        array<int,2> dp = {0,-oo};
        bool leaf=1;
        for(int to : adj[at]) if(to!=from) {
            leaf=0;
            auto cdp = self(self,to,at);
            array<int,2> ndp = {-oo,-oo};
            for(int i=0;i<2;++i) for(int j=0;j<2;++j) {
                ndp[i^j] = max(dp[i]+cdp[j],ndp[i^j]);
            }
            dp=ndp;
        }
        if(!leaf) dp[!a[at]]++;
        else dp = {a[at]==1,a[at]==0};
        return dp;

    };
    auto [r1,r2] = dfs(dfs,0,0);
    cout << max(r1,r2) << '\n';
}