#include<iostream>

#include<cstdio>

#include<cstring>

#include<algorithm>

#include<vector>

using namespace std;

int c[],d[] = {},n;

vector<int> v[];

void dfs(int x,int pre)

{

    for(int i = ;i < v[x].size();i++)

    {

        int t = v[x][i];

        if(t == pre)    continue;

        d[t] = d[x]+(c[x]^c[t]);

        dfs(t,x);

    }

}

int main()

{

    scanf("%d",&n);

    for(int i = ;i <= n;i++)   scanf("%d",&c[i]);

    for(int i = ;i < n;i++)

    {

        int a,b;

        scanf("%d%d",&a,&b);

        v[a].push_back(b);

        v[b].push_back(a);

    }

    dfs(,-);

    int t = ,maxx = d[];

    for(int i = ;i <= n;i++)

    {

        if(d[i] > maxx)

        {

            maxx = d[i];

            t = i;

        }

    }

    memset(d,,sizeof(d));

    dfs(t,-);

    maxx = d[];

    for(int i = ;i <= n;i++)

    {

        maxx = max(d[i],maxx);

    }

    printf("%d\n",(maxx+)/);

    return ;

}