#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<vector>
#include<queue>
#include<set>
#include<map>
#include<stack>
using namespace std;
const int maxn=50000+10;
vector<int>po[maxn];
int dep[maxn],ance[maxn][17],maxp[maxn][17],minp[maxn][17],maxi[maxn][17],maxI[maxn][17],price[maxn],n,fa[maxn];
bool vis[maxn];
int max(int a,int b)
{if(a>b)return a;else return b;
}
int min(int a,int b)
{if(a>b)return b;else return a;
}
queue<int> q;
void BFS_build()
{memset(vis,0,sizeof(vis));q.push(1);fa[1]=1;dep[1]=1;vis[1]=true;while(!q.empty()){int np=q.front();q.pop();ance[np][0]=fa[np];maxp[np][0]=max(price[np],price[fa[np]]);minp[np][0]=min(price[np],price[fa[np]]);if(price[np]<price[fa[np]])maxi[np][0]=price[fa[np]]-price[np];else maxi[np][0]=0;if(price[np]>price[fa[np]])maxI[np][0]=price[np]-price[fa[np]];else maxI[np][0]=0;for(int i=1;i<=16;i++)//倍增DP方程 {   ance[np][i]=ance[ance[np][i-1]][i-1];maxp[np][i]=max(maxp[np][i-1],maxp[ance[np][i-1]][i-1]);minp[np][i]=min(minp[np][i-1],minp[ance[np][i-1]][i-1]);int a=maxi[np][i-1],b=maxi[ance[np][i-1]][i-1],c=0;c=maxp[ance[np][i-1]][i-1]-minp[np][i-1];maxi[np][i]=max(max(a,b),c);a=maxI[np][i-1];b=maxI[ance[np][i-1]][i-1];c;c=maxp[np][i-1]-minp[ance[np][i-1]][i-1];maxI[np][i]=max(max(a,b),c);if(ance[np][i]==1)break;}for(int i=0;i<po[np].size();i++){int nv=po[np][i];if(vis[nv])continue;fa[nv]=np;dep[nv]=dep[np]+1;q.push(nv);vis[nv]=true;}}
}
int ia,ib,mi,ma;
int ancest;
void swim(int &a,int &b)
{if(dep[a]==dep[b])return ;while(dep[a]>dep[b]){int i;for(i=0;i<=16;i++){if(pow(2,i)+dep[b]>dep[a])break;}ia=max(max(ia,maxi[a][i-1]),maxp[a][i-1]-mi);mi=min(mi,minp[a][i-1]);a=ance[a][i-1];}while(dep[a]<dep[b]){int i;for(i=0;i<=16;i++){if(pow(2,i)+dep[a]>dep[b])break;}ib=max(max(ib,maxI[b][i-1]),ma-minp[b][i-1]);ma=max(ma,maxp[b][i-1]);b=ance[b][i-1];}
}
int solve(int a,int b)
{ia=0;ib=0;mi=price[a];ma=price[b];swim(a,b);if(a==b)return max(max(ia,ib),ma-mi);while(true){int i;for(i=0;i<=16;i++){if(ance[a][i]==ance[b][i])break;}if(i==0){ancest=ance[a][0];ia=max(ia,price[ancest]-mi);ib=max(ib,ma-price[ancest]);mi=min(mi,price[ancest]);ma=max(ma,price[ancest]);return max(max(ia,ib),ma-mi);}else{ia=max(max(ia,maxi[a][i-1]),maxp[a][i-1]-mi);ib=max(max(ib,maxI[b][i-1]),ma-minp[b][i-1]);mi=min(mi,minp[a][i-1]);ma=max(ma,maxp[b][i-1]);a=ance[a][i-1];b=ance[b][i-1];}}}
int main()
{freopen("t.txt","r",stdin);scanf("%d",&n);for(int i=1;i<=n;i++)scanf("%d",&price[i]);for(int i=1;i<n;i++){int a,b;scanf("%d%d",&a,&b);po[a].push_back(b);po[b].push_back(a);}BFS_build();int p;scanf("%d",&p);for(int i=1;i<=p;i++){int a,b;scanf("%d%d",&a,&b);printf("%d\n",solve(a,b)); }return 0;
}