dataer:
var
  n,m,i,j,k,x,y:longint;
begin
  assign(output,'1.in'); rewrite(output);
  readln(n,m); writeln(n); randomize;
  for i:=1 to n do writeln(random(50000)+1);
  for i:=2 to n do writeln(i,' ',random(i-1)+1); writeln(m);
  for i:=1 to m do writeln(random(n)+1,' ',random(n)+1);
end.

AC code:
{$inline on}
type
  edge=record
    x,y,next:longint;
  end;
  sets=record
    minv,maxv,tmax,bmax,father,v:longint;
  end;
var
  b,bb:array [0..100001] of edge;
  a,aa,ans,father:array [0..50001] of longint;
  v:array [0..50001] of boolean;
  c:array [0..50001] of sets;
  n,m,tot1,tot2:longint;
function max(x,y:longint):longint; inline;
begin
  if x>y then exit(x) else exit(y);
end;
function min(x,y:longint):longint; inline;
begin
  if x<y then exit(x) else exit(y);
end;
procedure addedge(x,y:longint);
begin
  inc(tot1);
  b[tot1].x:=y;
  b[tot1].next:=a[x];
  a[x]:=tot1;
end;
procedure addquestion(x,y,z:longint);
begin
  inc(tot2);
  bb[tot2].x:=y;
  bb[tot2].y:=z;
  bb[tot2].next:=aa[x];
  aa[x]:=tot2;
end;
procedure init;
var
  i,x,y:longint;
begin
  readln(n); tot1:=0; tot2:=0; fillchar(a,sizeof(a),0); fillchar(aa,sizeof(aa),0); fillchar(v,sizeof(v),true);
  for i:=1 to n do begin c[i].father:=i; readln(c[i].v); c[i].minv:=c[i].v; c[i].maxv:=c[i].v; end;
  for i:=1 to n-1 do begin readln(x,y); addedge(x,y); addedge(y,x); end; readln(m);
  for i:=1 to m do begin readln(x,y); addquestion(x,y,i); addquestion(y,x,i+m); end;
end;
function getfather(x:longint):longint;
var
  pre:longint;
begin
  if x=c[x].father then exit(x); pre:=c[x].father;
  c[x].father:=getfather(c[x].father);
  c[x].tmax:=max(c[pre].maxv-c[x].minv,max(c[pre].tmax,c[x].tmax));
  c[x].bmax:=max(c[x].maxv-c[pre].minv,max(c[pre].bmax,c[x].bmax));
  c[x].minv:=min(c[x].minv,c[pre].minv);
  c[x].maxv:=max(c[x].maxv,c[pre].maxv);
  exit(c[x].father);
end;
procedure union(x,y:longint);
begin
  x:=getfather(x); y:=getfather(y);
  c[y].father:=x;
end;
procedure dfs(x,pre:longint);
var
  p,pp,lca,minv,maxv,maxs,now:longint;
begin
  p:=a[x]; father[x]:=pre;
  while p<>0 do
  begin
    pp:=b[p].x; if pp=pre then begin p:=b[p].next; continue; end;
    dfs(pp,x); union(x,pp); p:=b[p].next;
  end;
  v[x]:=false; p:=aa[x];
  while p<>0 do
  begin
    pp:=bb[p].x; if v[pp] then begin p:=bb[p].next; continue; end;
    lca:=getfather(pp); minv:=c[x].v; maxv:=c[x].v; maxs:=0; now:=x;
    if bb[p].y<=m then
    begin
      while now<>lca do
      begin
        maxs:=max(maxs,c[now].v-minv);
        minv:=min(minv,c[now].v); now:=father[now];
      end;
      ans[bb[p].y]:=max(c[pp].maxv-minv,max(maxs,c[pp].bmax));
    end;
    if bb[p].y>m then
    begin
      while now<>lca do
      begin
        maxs:=max(maxs,maxv-c[now].v);
        maxv:=max(maxv,c[now].v); now:=father[now];
      end;
      ans[bb[p].y-m]:=max(maxv-c[pp].minv,max(maxs,c[pp].tmax));
    end;
    p:=bb[p].next;
  end;
end;
procedure main;
var
  i:longint;
begin
  for i:=1 to m do writeln(ans[i]);
end;
procedure openfile;
begin
  assign(input,'1.in');
  reset(input);
  assign(output,'1.out');
  rewrite(output);
end;
begin
  openfile;
  init;
  dfs(1,0);
  main;
end.