#include <bits/stdc++.h>
#define rep(i,l,r) for(int i=l; i<=r; i++)
#define per(i,r,l) for(int i=r; i>=l; i--)
#define IOS {cin.tie(0);cout.tie(0);ios::sync_with_stdio(0);}
using namespace std;

typedef long long ll;
typedef pair<int,int> P;

const int N = 100010;

int a[N], f[N][2];
vector<int> e[N];

void dfs(int u, int ff) {
    // , 
    int flag = 0;
    f[u][1] = -1e9;
    for (auto v: e[u]) {
        
        if (v == ff) continue;
        flag = 1;
        dfs(v, u);
        // if (u == 2) cout <<v<<"#";
        int tmp[2] = {0,0};
        tmp[0] = max(tmp[0], f[u][0] + f[v][0]);
        tmp[0] = max(tmp[0], f[u][1] + f[v][1]);
        tmp[1] = max(tmp[1], f[u][0] + f[v][1]);
        tmp[1] = max(tmp[1], f[u][1] + f[v][0]);
        
        // if (u == 1) {
            
        //     cout << v<<' '<<f[v][1]<<' '<<tmp[1] <<' '<<f[u][0]<<"$\n";
        // }
        f[u][0] = tmp[0];
        f[u][1] = tmp[1];
    }
    if (flag == 0) {
        f[u][0] = f[u][1] = 0;
    }
    if (a[u]) f[u][0]++;
    else f[u][1]++;
}

int main() {
    int n; scanf("%d", &n);
    rep (i, 1, n) {
        scanf("%d", &a[i]);
    }
    rep (i, 1, n-1) {
        int u, v; scanf("%d%d", &u, &v);
        e[u].push_back(v);
        e[v].push_back(u);
    }
    dfs(1, 0);
    // rep (i, 1, n) {
    //     cout << i<<' '<<f[i][0] <<' '<<f[i][1]<<endl;
    // }
    cout << max(f[1][0], f[1][1]);
    return 0;
}