program ploshchazakoordynatamy;
{$APPTYPE CONSOLE}
const t=2;
var a,b,c,d,e,f:integer; k,l,m,p:real;
f1,f2:text;
begin
assign(f1,'input.txt');
reset(f1);
readln(f1,a);
readln(f1,b);
readln(f1,c);
readln(f1,d);
readln(f1,e);
readln(f1,f);
assign(f2,'output.txt');
rewrite(f2);
k:=sqrt(sqr(b-a)+sqr(d-c));
l:=sqrt(sqr(b-a)+sqr(f-e));
m:=sqrt(sqr(f-e)+sqr(d-c));
if (k+l>m) and (k+m>l) and (l+m>k) then begin
p:=(k+l+m)/t;
p:=sqrt(p*(p-k)*(p-l)*(p-m));
writeln(f2,p:8:2);
end;
if (k+l<m) and (k+m<l) and (l+m<k) then
writeln(f2,'ce ne trykutnyk');
close(f1);
close(f2);
end.