Here's my source code:

{$r+,n+,q+,b-}
const maxn=10000;
var x,y:array[1..maxn] of longint;
    a:array[1..maxn] of real;
    b:array[1..maxn] of integer;
    n:integer;
    min,a1,a2:longint;

procedure nhap;
var i:integer;
begin
   readln(n);
   min:=maxlongint;
   for i:=1 to n do
   begin
      readln(x[i],y[i]);
      if (y[i]<min) or ((y[i]=min) and (x[i]>x[a1])) then
      begin
         min:=y[i];
         a1:=i;
      end;
   end;
end;

procedure shellsort;
var i,j,h,tb:integer;
    ta:real;
begin
   h:=n shr 1;
   while h<>0 do
   begin
      for i:=h+1 to n do
      begin
         ta:=a[i]; tb:=b[i];
         j:=i-h;
         while (j>0) and (a[j]>ta) do
         begin
            a[j+h]:=a[j];
            b[j+h]:=b[j];
            j:=j-h;
         end;
         a[j+h]:=ta;
         b[j+h]:=tb;
      end;
      h:=h shr 1;
   end;
end;

function angle(i,j:integer):real;
var dx,dy,ax,ay:longint;
    t:real;
begin
   dx:=x[j]-x[i]; ax:=abs(dx);
   dy:=y[j]-y[i]; ay:=abs(dy);
   if (dx=0) and (dy=0) then t:=0 else t:=dy/(ax+ay);
   if dx<0 then t:=2-t else if dy<0 then t:=4+t;
   angle:=t*90;
end;

procedure init;
var i:integer;
begin
   for i:=1 to n do a[i]:=angle(a1,i);
   for i:=1 to n do b[i]:=i;
end;

begin
   nhap;
   init;
   shellsort;
   writeln(a1,' ',b[n div 2+1]);
end.