program aa;
var
 x,r,e,f,g,h,v,i,t1,t2,j,max:longint;
 f1,f2:text;
 sum,a,b,c,m,d,mmm:real;
 l:array[1..1000000,1..2] of real;
begin
 assign(f1,'sars.in');
 assign(f2,'sars.out');
 reset(f1);
 rewrite(f2);
 readln(f1,l[1,1],r,m,v);
 t1:=1;t2:=2;
 j:=0;i:=1;max:=0;mmm:=m*2;  j:=j-v;
 while mmm>=1 do
 begin
  h:=1;
  for e:=1 to i do
   if (l[e,t1]+r+0.00001>=j)and(l[e,t1]-r-0.00001<=j) then begin inc(max); break; end;
  j:=j+v;
  for e:=1 to i do
  begin
   l[h,t2]:=l[e,t1]+m;
   inc(h);
   if l[e,t1]>=j then
   l[h,t2]:=l[e,t1]-m;
   inc(h);
  end;
  m:=m/2;
  mmm:=mmm/2;
  if t1=1 then begin t1:=2; t2:=1; end else begin t1:=1; t2:=2; end;
  i:=h-1;
 end;
 writeln(f2,max);
 close(f1);close(f2);
end.