var     a:array[1..100000] of longint;
        b:array[1..1000000000] of char;
        n,m,i,j,t,u,v:longint;
        c:char;
        s:string;
        f,g:text;
begin
  assign(f,'lca1.in');
  assign(g,'lca.out');
  reset(f);
  rewrite(g);
  settextbuf(f,b);
  settextbuf(g,b);
  readln(f,n,m);
  a[1]:=0;
{  for i:=2 to n do
    read(f,a[i]);}
  i:=2;
  while not eoln(f) do
    begin
      read(f,s);
      for j:=1 to length(s) do
        if s[j]=' ' then inc(i) else a[i]:=a[i]+ord(s[j])-ord('0');
    end;

  for i:=1 to m do
    begin
      readln(f,u,v);
      while u<>v do
        if u>v then u:=a[u] else v:=a[v];
      writeln(g,v);
    end;
  close(g);
end.