Can't you just ask for idea - not solution! I have solved each of
these problems, and I'll be glad to help you with any of them,
without asking anything in return! But program exchange is really
wierd and useless!

> Can't you just ask for idea - not solution! I have solved each of
> these problems, and I'll be glad to help you with any of them,
> without asking anything in return! But program exchange is really
> wierd and useless!

..Or find test where my program failed.

Program t1159;{$N+}

Const MaxN   = 100;
      Change = 180/Pi;
      OkW    = 360.0;
      Eps    = 1E-15;
      Eps2   = 1E-1;

Var   Block        : array[1..MaxN]of integer;
      N,i,sum,max  : integer;
      mx,t         : integer;
      left,rigth   : extended;
      middle,pk    : extended;
      curW,p       : extended;
      ok           : boolean;
      label          AAA;

Function GetLW(R : extended;L : integer) : extended;
Var cosw,w,tgw  : extended;
 begin
  cosw:=(2*R*R-L*L)/(2*R*R);
  if cosw=0 then w:=90 else begin
    tgw:=sqrt(1-cosw*cosw)/cosw;
    w:=ArcTan(tgw)*Change;
    if w<0 then w:=180+w;
   end;
  GetLW:=w;
 end;

Function GetW(R : extended) : extended;
Var w     : extended;
    j     : integer;
 begin
  w:=0;
  for j:=1 to N do w:=w+GetLW(R,Block[j]);
  GetW:=w;
 end;

Function GetS(R : extended) : extended;
Var Ans,p,S  : extended;
    i        : integer;
 begin
  Ans:=0;
  for i:=1 to N do begin
    p:=(2*R+Block[i])/2;
    S:=sqrt(abs(p*(p-R)*(p-R)*(p-Block[i])));
    Ans:=Ans+S;
   end;
  GetS:=Ans;
 end;

Procedure WriteAns(R : extended);
 begin
  Writeln(GetS(R):0:2);
  Halt(0);
 end;

Procedure WriteAns2(R : extended);
Var S,p  : extended;
 begin
  p:=(R+R+Block[N+1])/2;
  S:=sqrt(p*(p-R)*(p-R)*(p-Block[N+1]));
  Writeln(GetS(R)-S:0:2);
  Halt(0);
 end;

begin
 Read(N);
 sum:=0;
 max:=0;
 for i:=1 to N do Read(Block[i]);
 for i:=1 to N do begin
   sum:=sum+Block[i];
   if Block[i]>max then begin
    max:=Block[i];
    mx:=i;
   end;
  end;
 if mx<>N then begin
   t:=Block[mx];
   Block[mx]:=Block[N];
   Block[N]:=t;
  end;
 if max>=sum-max then begin
   Block[N]:=1;
   Writeln('0.00');
   Halt(0);
  end;
 pk:=max/2;
 left:=pk;
 rigth:=sum;
 While True do begin
   middle:=(left+rigth)/2;
   curW:=GetW(middle);
   if curW<OkW then rigth:=middle else left:=middle;
   if rigth-left<Eps then break;
  end;
 if abs(curW-OkW)<Eps2 then WriteAns(middle);
 N:=N-1;
 left:=pk;
 rigth:=1E10;
 While True do begin
   middle:=(left+rigth)/2;
   curW:=GetW(middle);
   if curW>GetLW(middle,Block[N+1]) then rigth:=middle else
left:=middle;
   if rigth-left<Eps then break;
  end;
 if abs(GetW(middle)-GetLW(middle,Block[N+1]))<Eps2 then writeans2
(middle);
end.

Try this test case:
4
1
2
3
5
The correct answer is 4.44

Good luck!

> Try this test case:
> 4
> 1
> 2
> 3
> 5
> The correct answer is 4.44
>
> Good luck!