begin
  boolean Debugging = false;
  real    Pi        = 3.14159265;
  

  procedure Debug(T);
    text T;
  begin
    if Debugging then begin
      OutText("Debug> " & T);  OutImage;
    end if;
  end Debug;


  real procedure Degrees(Rad);
    real Rad;
  begin
    Degrees := Rad/Pi * 180;
  end Degrees;


  real procedure Solve(NHooks, RopeLength);
    integer NHooks;
    real    RopeLength;
  begin
    ref(Hook) array H(0:NHooks+1);

    class Hook(X, Y);
      real X, Y;
    begin
      real procedure Dir(H2);
        ref(Hook) H2;
      begin
	real dX, dY, D;

	dX := H2.X-X;  dY := H2.Y-Y;
	D := if dX=0 then 90 else Degrees(ArcTan(dY/dX));
	if dX < 0 then D := D+180;
	Dir := D;
      end Dir;

      procedure Dump;
      begin
	OutText("(");  OutFix(X, 2, 0);
	OutText(",");  OutFix(Y, 2, 0);  OutText(")");
      end Dump;

      real procedure FindNext(CurDir, CurLen);
        real CurDir, CurLen;
      begin
	ref(Hook) BestHook;
	real      BestDir, BestDist, BestAngle;
	integer   I;

	if Y >= -CurLen then begin
	  H(NHooks+1) :- new Hook(X+Sqrt(CurLen**2-Y**2),0);
	end else begin
	  H(NHooks+1) :- none;
	end if;
	
	for I := 0 step 1 until NHooks+1 do begin
	  if H(I)=/=none and then H(I)=/=this Hook then begin
	    boolean procedure BetterHook;
	    begin
	      if L <= CurLen*1.0001 then begin
		if BestHook =/= none then begin
		  if A < BestAngle then BetterHook := true else
		  if A=BestAngle and L>BestDist then BetterHook := true;
		end else BetterHook := true;
	      end if;
	    end BetterHook;

	    real A, D, L;

	    D := Dir(H(I));  L := Length(H(I));  A := D-CurDir;
	    if A < 0 then A := A+360;

	    if Debugging then begin
	      OutText("Debug: ");  Dump;  OutText(" and ");  H(I).Dump;
	      OutText(": Dir=");  OutFix(D, 2, 0);
	      OutText(", Angle=");  OutFix(A, 2, 0);
	      OutText(", Distance=");  OutFix(L, 2, 0);  OutImage;
	    end if;
	    
	    if BetterHook then begin
	      BestHook :- H(I);  BestAngle := A;  BestDir := D;
	      BestDist := L;
	    end if;
	  end if;
	end for;
	
	if BestHook == none then begin
	  if Debugging then begin
	    Debug("Pendulum has started circling around a hook.");
	    OutText("       Circumference is 2*Pi*");  OutFix(CurLen,2,0);
	    OutText(" = ");  OutFix(2*Pi*CurLen,2,0);  OutImage;
	  end if;

	  FindNext := -2*Pi*CurLen;
	end else
	if BestHook == H(NHooks+1) then begin
	  if Debugging then begin
	    Debug("Pendulum has reached its highest point.");
	    OutText("       Length of last arc is 2*Pi*");  OutFix(CurLen,2,0);
	    OutText("*");  OutFix(BestAngle,2,0);  OutText("/360 = ");
	    OutFix(2*Pi*CurLen*BestAngle/360,2,0);  OutImage;
	  end if;

	  FindNext := 2*2*Pi*CurLen*BestAngle/360;
	end else begin
	  real NextD;

	  if Debugging then begin
	    Debug("Pendulum bends around a hook and continues.");
	    OutText("       Free rope is now ");  
	    OutFix(CurLen-BestDist,2,0);  OutImage;
	  end if;

	  NextD := BestHook.FindNext(BestDir,CurLen-BestDist);

	  if Debugging and NextD>=0 then begin
	    OutText("       Length of previous arc is 2*Pi*");
	    OutFix(CurLen,2,0);  OutText("*");  OutFix(BestAngle,2,0);
	    OutText("/360 = ");
	    OutFix(2*Pi*CurLen*BestAngle/360,2,0);  OutImage;
	  end if;

	  FindNext := if NextD<0 then NextD else 
	                              NextD + 2*2*Pi*CurLen*BestAngle/360;
	end if;
      end FindNext;

      real procedure Length(Hx);
        ref(Hook) Hx;
      begin
	Length := Sqrt((Hx.X-X)**2 + (Hx.Y-Y)**2);
      end Length;
    end Hook;

    integer I;

    H(0) :- new Hook(0,0);
    for I := 1 step 1 until NHooks do H(I) :- new Hook(InF.InInt,InF.InInt);
    
    Solve := Abs(H(0).FindNext(180,RopeLength));
  end Solve;


  ref(InFile)  InF;
  ref(OutFile) OutF;
  integer      NHooks, Cnt;
  real         Res;

  InF  :- new InFile ("pendulum.in");    InF.Open(Blanks(80));
  OutF :- new OutFile("pendulum.out");  OutF.Open(Blanks(80));

  for NHooks := InF.InInt while NHooks > 0 do begin
    Debug("New pendulum:");

    Res := Solve(NHooks, InF.InReal);  Cnt := Cnt+1;
    inspect OutF do begin
      OutText("Pendulum #");  OutInt(Cnt, 0);  OutImage;
      OutText("Length of periodic orbit = ");  OutFix(Res, 2, 0);  OutImage;
      OutImage;
    end inspect;
  end for;

  InF.Close;  OutF.Close;
end