var n,m,i:longint;
    a:array[0..500000]of longint;
    u:array[0..10000000]of boolean;
begin
 readln(n);
 fillchar(u,sizeof(u),false);
 a[0]:=0; a[1]:=1;
 u[0]:=true; u[1]:=true;
 m:=2;
 while m<=n do begin
  if (a[m-1]-m>0)and(u[a[m-1]-m]=false)
  then begin a[m]:=a[m-1]-m; u[a[m]]:=true;end
  else begin a[m]:=a[m-1]+m; u[a[m]]:=true;end;
 inc(m);
 end;
 writeln(a[n]);
close(input);
close(output);
end.