#include <iostream>
#include <cstdio>
#include <cstring>
#include <queue>
#include <vector>
#define MAX 50001
using namespace std;
int n,m;
int ne;
struct edge
{
    int from,to,next;
    int weight;
}P[MAX*2];
int w[MAX],deep[MAX];
int visit[MAX];
int head[MAX*2];
int parent[MAX];
int f[MAX][20],fmax[MAX][20],fmin[MAX][20],fdmax[MAX][20],fdmin[MAX][20];
void insert(int x,int y,int weight)
{
    P[ne].from=x;P[ne].to=y;P[ne].weight=weight;P[ne].next=head[x];head[x]=ne++;
    P[ne].from=y;P[ne].to=x;P[ne].weight=weight;P[ne].next=head[y];head[y]=ne++;
}
void dfs(int now,int fa,int step)
{
    int i,j;
    int next;
    visit[now]=true;
    deep[now]=step;
    parent[now]=fa;
    for(i=0;(1<<i)<=deep[now]+1;i++)
    if(f[now][i - 1] != - 1)
    {
        f[now][i] = f[f[now][i - 1]][i - 1];
        if(f[now][i]==-1) continue;
        fmax[now][i] = max(fmax[now][i - 1], fmax[f[now][i - 1]][i - 1]);
        fmin[now][i] = min(fmin[now][i - 1], fmin[f[now][i - 1]][i - 1]);
        fdmax[now][i] = max(fdmax[f[now][i - 1]][i - 1],max(fdmax[now][i - 1],fmax[f[now][i - 1]][i - 1] - fmin[now][i - 1]));
        fdmin[now][i] = min(fdmin[f[now][i - 1]][i - 1],min(fdmin[now][i - 1],fmin[f[now][i - 1]][i - 1] - fmax[now][i - 1]));
    }
    for(i=head[now];i+1;i=P[i].next)
    {
        next=P[i].to;
        if(visit[next]) continue;
        f[next][0]=now;
        fmax[next][0]=max(w[now],w[next]);
        fmin[next][0]=min(w[now],w[next]);
        fdmax[next][0]=w[now]-w[next];
        fdmin[next][0]=w[now]-w[next];
        dfs(next,now,step+1);
    }
}
int LCA(int a,int b)
{
    int i,j;
    if(deep[a]<deep[b]) swap(a,b);
    i=0;
    while(deep[a]>=(1<<i))
    i++;
    i--;
    for(j=i;j>=0;j--)
    if(deep[a]-(1<<j)>=deep[b])
    a=f[a][j];
    if(a==b)
    return a;
    for(j=i;j>=0;j--)
    if(f[a][j]!=-1&&f[a][j]!=f[b][j])
    {
        a=f[a][j];
        b=f[b][j];
    }
    return parent[a];
}
int bb[2][35];
bool flg[35];
void get_max_min(int a,int b,int &ma,int &mi,int &mca,int &mci)
{
    int i,j;
    memset(flg,0,sizeof flg);
    ma = mi = w[a];
    mca = mci = w[b] - w[a];
    for(i = deep[a] - deep[b],j = 0; i; i >>= 1, ++ j) if(i & 1)
    {
        ma = max(ma,fmax[a][j]);
        mi = min(mi,fmin[a][j]);
        mca = max(mca,fdmax[a][j]);
        mci = min(mci,fdmin[a][j]);
        bb[0][j] = fmax[a][j];
        bb[1][j] = fmin[a][j];
        flg[j] = 1;
        a = f[a][j];
    }
    for(i = 16 - 1; i > 0; -- i)
    for(j = i - 1; j >= 0; -- j)
    if(flg[i] && flg[j])
    {
        mca = max(mca,bb[0][i] - bb[1][j]);
        mci = min(mci,bb[1][i] - bb[0][j]);
    }
}
int main()
{
    int i,j;
    int x,y,weight;
    memset(head,-1,sizeof head);
    ne=2;
    memset(f,-1,sizeof(f));
    memset(fmax,0xfc,sizeof fmax);
    memset(fmin,0x7f,sizeof fmin);
    memset(fdmax,0xfc,sizeof fdmax);
    memset(fdmin,0x7f,sizeof fdmin);
    memset(visit,0,sizeof(visit));
    scanf("%d",&n);
    for(i=1;i<=n;i++)
    scanf("%d",&w[i]);
    for(i=1;i<=n-1;i++)
    {
        scanf("%d%d",&x,&y);
        insert(x,y,1);
    }
    dfs(1,-1,0);
    scanf("%d",&m);
    while(m--)
    {
        scanf("%d%d",&x,&y);
        int c=LCA(x,y);
        int ma[2],mi[2],mca[2],mci[2],ans = 0;
        get_max_min(x,c,ma[0],mi[0],mca[0],mci[0]);
        get_max_min(y,c,ma[1],mi[1],mca[1],mci[1]);
        ans = max(0,max(mca[0], - mci[1]));
        ans = max(ans,ma[1] - mi[0]);
        printf("%d\n",ans);
    }
    return 0;
}