1 type node=record x,y:longint; end;
2 const maxn=3008;
3 var k,q,qq:longint;
4 sum:double;
5 f,g:array[0..maxn] of node;
6 m,i,j,a,b:longint;
7 stack:array[0..maxn] of longint;
8 nm:longint;
9 function dis(a,b:node):double;
10 begin
11 exit(sqrt(sqr(a.x-b.x)+sqr(a.y-b.y)));
12 end;
13 procedure swap(var a,b:node); inline;
14 var c:node;
15 begin
16 c:=a; a:=b; b:=c;
17 end;
18 function dig(a,b:node):longint; inline;
19 begin
20 exit(a.x*b.y-a.y*b.x);
21 end;
22 function mk(a,b:node):node; inline;
23 begin
24 mk.x:=b.x-a.x;
25 mk.y:=b.y-a.y;
26 end;
27 function cmp(a,b:node):boolean; inline;
28 var p1,p2:node;
29 begin
30 p1:=mk(f[1],a);
31 p2:=mk(f[1],b);
32 if dig(P1,P2)<0 then exit(true);
33 if dig(P1,P2)=0 then
34 if dis(f[1],a)>dis(f[1],b) then
35 exit(true);
36 exit(false);
37 end;
38 procedure sort(l,r:longint);
39 var i,j:longint;
40 x:node;
41 begin
42 i:=l; j:=r; x:=f[(l+r) div 2];
43 while i<=j do
44 begin
45 while cmp(f[i],x) do inc(i);
46 while cmp(x,f[j]) do dec(j);
47 if i<=j then
48 begin
49 swap(f[i],f[j]);
50 inc(i); dec(j);
51 end;
52 end;
53 if l<j then sort(l,j);
54 if i<r then sort(i,r);
55 end;
56 begin
57 readln(q);
58 for qq:=1 to q do
59 begin
60 readln(m);
61 for i:=1 to m do readln(f[i].x,f[i].y);
62 if m=2 then begin writeln('0.0'); continue; end;
63 j:=1;
64 for i:=2 to m do
65 if (f[i].y<f[j].y) or (f[i].y=f[j].y) and (f[i].x<f[j].x) then
66 j:=i;
67 swap(f[1],f[j]);
68 sort(2,m);
69 k:=2;
70 g[1]:=f[1]; g[2]:=f[2];
71 for i:=3 to m do
72 if dig(mk(f[1],f[i]),mk(f[1],f[i-1]))<>0 then
73 begin
74 inc(k);
75 g[k]:=f[i];
76 end;
77 nm:=3;
78 stack[1]:=1; stack[2]:=2; stack[3]:=3;
79 for i:=4 to k do
80 begin
81 a:=stack[nm-1];
82 b:=stack[nm];
83 while dig(mk(g[a],g[b]),mk(g[a],g[i]))>0 do
84 begin
85 dec(nm);
86 a:=stack[nm-1];
87 b:=stack[nm];
88 end;
89 inc(nm);
90 stack[nm]:=i;
91 end;
92 sum:=0;
93 while nm>=3 do
94 begin
95 a:=stack[nm];
96 b:=stack[nm-1];
97 sum:=sum+abs(dig(mk(g[1],g[b]),mk(g[1],g[a])))/2;
98 dec(nm);
99 end;
100 writeln(sum:0:1);
101 end;
102 end.
