#include<cstdio>
#include<iostream>
#include<vector>
#define RI register int
#define CI const int&
using namespace std;
const int N=100005;
int n,a[N],x,y,f[N][2]; vector <int> v[N];
inline void DFS(CI now=1,CI fa=0)
{
    bool flag=1;
    for (auto to:v[now]) if (to!=fa)
    {
        DFS(to,now);
        if (flag)
        {
            for (RI i=0;i<2;++i) f[now][i]=f[to][i]; flag=0;
        } else
        {
            int g[2]={0,0};
            for (RI p=0;p<2;++p) for (RI q=0;q<2;++q)
            g[p^q]=max(g[p^q],f[now][p]+f[to][q]);
            for (RI i=0;i<2;++i) f[now][i]=g[i];
        }
    }
    ++f[now][a[now]^1];
}
int main()
{
    scanf("%d",&n);
    for (RI i=1;i<=n;++i) scanf("%d",&a[i]);
    for (RI i=1;i<n;++i) scanf("%d%d",&x,&y),v[x].push_back(y),v[y].push_back(x);
    DFS(),printf("%d",max(f[1][0],f[1][1]));
    //for (RI i=1;i<=n;++i) printf("f[%d][0] = %d; f[%d][1] = %d\n",i,f[i][0],i,f[i][1]);
    return 0;
}