var n,x,r:integer;
    y2,y,s:int64;

BEGIN
s:=0;
read (n);
r:=n;

 for x:=0 to n-1 do
  begin
   y:=trunc(sqrt(r-x)*sqrt(r+x));

     if y*y<>(r-x)*(r+x) then y:=y+1;

    s:=s+y;
  end;

writeln (s*4);
END.