#include <stdio.h>
#define MAXN 50010
int n, h[MAXN], d[MAXN*2], p[MAXN*2];
int depth[MAXN], price[MAXN];
int upper[MAXN][16], maxprice[MAXN][16], minprice[MAXN][16];
int getmax(int a, int b)
{
  int ans=a, i;
  for (i=15; i>=0; --i)
    {
      if (depth[a]-(1<<i)>=depth[b])
        {
          if (price[maxprice[a][i]]>price[ans])
            ans=maxprice[a][i];
          a=upper[a][i];
        }
    }
  if (price[b]>price[ans])
    ans=b;
  return ans;
}
int getmin(int a, int b)
{
  int ans=a, i;
  for (i=15; i>=0; --i)
    {
      if (depth[a]-(1<<i)>=depth[b])
        {
          if (price[minprice[a][i]]<price[ans])
            ans=minprice[a][i];
          a=upper[a][i];
        }
    }
  if (price[b]<price[ans])
    ans=b;
  return ans;
}
int maxprofit(int a, int b, int c)
{
  int ans=0, i1, i2;
  i1=getmin(a,c);
  i2=getmax(i1,c);
  if (price[i2]-price[i1]>ans)
    ans=price[i2]-price[i1];
  i2=getmax(b,c);
  i1=getmin(i2,c);
  if (price[i2]-price[i1]>ans)
    ans=price[i2]-price[i1];
  i1=getmin(a,c);
  i2=getmax(b,c);
  if (price[i2]-price[i1]>ans)
    ans=price[i2]-price[i1];
  return ans;
}
int searchup(int a, int b)
{
  int i;
  for (i=15; i>=0; --i)
    {
      if (depth[a]-(1<<i)>=depth[b])
        a=upper[a][i];
    }
  for (i=15; i>=0; --i)
    {
      if (depth[b]-(1<<i)>=depth[a])
        b=upper[b][i];
    }
  if (a!=b)
    {
      for (i=15; i>=0; --i)
        {
          if (upper[a][i]!=upper[b][i])
            {
              a=upper[a][i];
              b=upper[b][i];
            }
        }
      a=upper[a][0];
      b=upper[b][0];
    }
  return a;
}
void addedge(int id, int a, int b)
{
  d[id]=b;
  p[id]=h[a];
  h[a]=id;
}
void dfs(int id, int level)
{
  int i, j;
  depth[id]=level;
  for (i=h[id]; i!=0; i=p[i])
    {
      j=d[i];
      if (depth[j]==0)
        {
          upper[j][0]=id;
          dfs(j,level+1);
        }
    }
}
int main()
{
#ifndef ONLINE_JUDGE
freopen("poj3728.in","r",stdin);
#endif
  int i, j, a, b, q;
  scanf("%d",&n);
  for (i=1; i<=n; ++i) scanf("%d", &price[i]);
  for (i=1; i<=n-1; ++i)
    {
      scanf("%d%d", &a, &b);
      addedge(i*2-1,a,b);
      addedge(i*2,b,a);
    }
  dfs(1,1);
  for (i=1; i<=n; ++i)
    {
      minprice[i][0]=i;
      maxprice[i][0]=i;
    }
  for (j=1; j<=15; ++j)
    {
      for (i=1; i<=n; ++i)
        {
          a=upper[i][j-1];
          b=upper[a][j-1];
          upper[i][j]=b;
          minprice[i][j]=(price[minprice[i][j-1]]<=price[minprice[a][j-1]]?minprice[i][j-1]:minprice[a][j-1]);
          maxprice[i][j]=(price[maxprice[i][j-1]]>=price[maxprice[a][j-1]]?maxprice[i][j-1]:maxprice[a][j-1]);
        }
    }
  for (scanf("%d",&q); q; --q)
    {
      scanf("%d%d",&a,&b);
      printf("%d\n", maxprofit(a,b,searchup(a,b)));
    }
  return 0;
}