看不出来哪儿错了，麻烦众佬指出

#include<bits/stdc++.h>
#include<cmath>
using namespace std;
double jl(double x1, double y1, double x2, double y2)
{
	return sqrt(abs((x1 - x2) * (x1 - x2)) + abs((y1 - y2) * (y1 - y2)));
}
int main( )
{
	double x1,x2,x3,y1,y2,y3;
	double a,b,c,p,s;
	cin>>x1>>y1>>x2>>y2>>x3>>y3;
	a=jl(x1,y1,x2,y2);
	b=jl(x1,y1,x3,y3);
	c=jl(x2,y2,x3,y3);
	p=(a+b+c)/2;
	s=sqrt(p*(p-a)*(p-b)*(p-c));
	printf("%.3lf",s);
	return 0;
}