#include <bits/stdc++.h>
using namespace std;
#define int ll
#define ll long long
#define pii pair<int,int>
#define fs first
#define sc second
const int mxn = 2e5+10;
vector<int> op[mxn],tree[mxn];
vector<pii> ctree[mxn];
int N;
int arr[mxn],brr[mxn];
struct SEG{
pii seg[mxn*4];
void modify(int now,int l,int r,int p,int v){
if(l == r){
seg[now] = make_pair(v,l);
return;
}
int mid = (l+r)>>1;
if(mid>=p)modify(now*2+1,l,mid,p,v);
else modify(now*2+2,mid+1,r,p,v);
seg[now] = max(seg[now*2+1],seg[now*2+2]);
}
pii getbig(int now,int l,int r,int s,int e){
if(l>=s&&e>=r)return seg[now];
int mid = (l+r)>>1;
if(mid>=e)return getbig(now*2+1,l,mid,s,e);
else if(mid<s)return getbig(now*2+2,mid+1,r,s,e);
else return max(getbig(now*2+1,l,mid,s,e),getbig(now*2+2,mid+1,r,s,e));
}
SEG(){
memset(seg,0,sizeof(seg));
}
};
SEG seg;
queue<int> q;
void cbuild(int now,int l,int r){
if(now != l){
int ls = seg.getbig(0,1,N,l,now-1).sc;
ctree[now].push_back({ls,abs(ls-now)});
cbuild(ls,l,now-1);
}
if(now != r){
int rs = seg.getbig(0,1,N,now+1,r).sc;
ctree[now].push_back({rs,abs(rs-now)});
cbuild(rs,now+1,r);
}
return;
}
int dfs(int now){
int dp = 0;
for(auto nxt:ctree[now]){
dp = max(dp,dfs(nxt.fs)+nxt.sc);
}
return dp;
}
main(){
ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
cin>>N;
for(int i = 1;i<=N;i++)cin>>arr[i],brr[i] = i;
for(int i = 1;i<N;i++){
int a,b;
cin>>a>>b;
tree[a].push_back(b);
tree[b].push_back(a);
}
for(int i = 1;i<=N;i++)seg.modify(0,1,N,i,arr[i]);
int rt = seg.getbig(0,1,N,1,N).sc;
cbuild(rt,1,N);
cout<<dfs(rt);
}
