Program Lx;
Var
  t, n, k, Max, i, j: Longint;
  a: Array[1..1000000] Of Longint;
  b: Array[0..1000000] Of Boolean;
  f: Boolean;
Begin
  Readln(t);
  For i:=1 to t Do Begin
    Readln(n);
    Max := 0;
    For i:=1 To n Do Begin
      Read(a[i]);
      If (a[i] > Max) Then Max := a[i];
    End;
    Readln;
    For k:=1 To Max Do Begin
      f := True;
      Fillchar(b, Sizeof(b), False);
      For i:=1 To n Do Begin
        If (b[a[i] Mod k]) Then Begin f := False; Break; End;
        b[a[i] Mod k] := True;
      End;
      If (f) Then Begin Writeln(k); Break; End; 
    End;
  End;
End.