const oo= shl ;

       eps=1e-8;

 var i,j,k,m,n:longint;

     x,y:array[..] of longint;

     z:array[..] of double;

     ans,xx,yy:int64;

 procedure swap(var a,b:longint);

   var c:longint;

   begin

     c:=a;

     a:=b;

     b:=c;

   end;

 procedure sort(l,r:longint);

   var i,j:longint;

       p,q:double;

   begin

     i:=l; j:=r;

     p:=z[(l+r) shr ];

     repeat

       while z[i]<p-eps do inc(i);

       while z[j]>p+eps do dec(j);

       if i<=j then

       begin

         swap(x[i],x[j]);

         swap(y[i],y[j]);

         q:=z[i]; z[i]:=z[j]; z[j]:=q;

         inc(i); dec(j);

       end;

     until i>j;

     if l<j then sort(l,j);

     if i<r then sort(i,r);

   end;

 begin

   readln(n);

   for i:= to n do

     readln(x[i],y[i]);

   for i:= to n- do

   begin

     k:=i;

     for j:=i to n do

       if x[j]<x[k] then k:=j;

     swap(x[i],x[k]);

     swap(y[i],y[k]);

     for j:=i+ to n do

       if x[j]=x[i] then

         if y[j]>y[i] then z[j]:=oo

         else z[j]:=-oo

       else z[j]:=(y[j]-y[i])/(x[j]-x[i]);

     sort(i+,n);

     xx:=; yy:=;

     for j:=i+ to n do

     begin

       ans:=ans+(x[j]-x[i])*yy-(y[j]-y[i])*xx;

       xx:=xx+x[j]-x[i]; yy:=yy+y[j]-y[i];

     end;

   end;

   writeln(abs(ans)/::);

 end.