#include<cstdio>

 #include<algorithm>

 #define lson ls[x],L,mid

 #define rson rs[x],mid+1,R

 #define rep(i,l,r) for (int i=(l); i<=(r); i++)

 #define For(i,x) for (int i=h[x],k; i; i=nxt[i])

 using namespace std;

 const int N=;

 int n,u,v,ans,nd,cnt,tot,lis[N*],lds[N*],ls[N*],rs[N*];

 int h[N],to[N<<],nxt[N<<],rt[N],a[N],b[N];

 void add(int u,int v){ to[++cnt]=v; nxt[cnt]=h[u]; h[u]=cnt; }

 int merge(int x,int y){

     if (!x || !y) return x|y;

     lis[x]=max(lis[x],lis[y]); lds[x]=max(lds[x],lds[y]);

     ans=max(ans,max(lis[ls[x]]+lds[rs[y]],lds[rs[x]]+lis[ls[y]]));

     ls[x]=merge(ls[x],ls[y]); rs[x]=merge(rs[x],rs[y]); return x;

 }

 void mdf(int &x,int L,int R,int p,int k,int a[]){

     if (!x) x=++nd;

     a[x]=max(a[x],k); int mid=(L+R)>>;

     if (L==R) return;

     if (p<=mid) mdf(lson,p,k,a); else mdf(rson,p,k,a);

 }

 int que(int x,int L,int R,int l,int r,int a[]){

     if (L==l && r==R) return a[x];

     int mid=(L+R)>>;

     if (r<=mid) return que(lson,l,r,a);

     else if (l>mid) return que(rson,l,r,a);

         else return max(que(lson,l,mid,a),que(rson,mid+,r,a));

 }

 void dfs(int x,int fa){

     For(i,x) if ((k=to[i])!=fa) dfs(k,x);

     int s1=,s2=,t1,t2;

     For(i,x) if ((k=to[i])!=fa){

         t1=a[x]> ? que(rt[k],,tot,,a[x]-,lis) : ;

         t2=a[x]<tot ? que(rt[k],,tot,a[x]+,tot,lds) : ;

         rt[x]=merge(rt[x],rt[k]); ans=max(ans,max(s1+t2+,s2+t1+));

         s1=max(s1,t1); s2=max(s2,t2);

     }

     mdf(rt[x],,tot,a[x],s1+,lis); mdf(rt[x],,tot,a[x],s2+,lds);

 }

 int main(){

     freopen("490F.in","r",stdin);

     freopen("490F.out","w",stdout);

     scanf("%d",&n);

     rep(i,,n) scanf("%d",&a[i]),b[i]=a[i];

     sort(b+,b+n+); tot=unique(b+,b+n+)-b-;

     rep(i,,n) a[i]=lower_bound(b+,b+tot+,a[i])-b;

     rep(i,,n) scanf("%d%d",&u,&v),add(u,v),add(v,u);

     dfs(,); printf("%d\n",ans);

     return ;

 }