#include<bits/stdc++.h>
using namespace std;using db=double;
using cp=complex<db>;
cp a,b,c,d;
void read(cp &x){
	int a,b;scanf("%d%d",&a,&b);
	x=cp(a,b);
}
db dist(cp x,cp y){
	x-=y;
	return sqrt(x.imag()*x.imag()+x.real()*x.real());
}
void Solve(){
	read(a);read(b);read(c);read(d);
	cp m1=(a+b)/2.0,m2=(c+d)/2.0;
	// cerr<<dist(c,m2)<<'\n';
	printf("%.10lf\n",fabs(m1.real()-m2.real())+fabs(m1.imag()-m2.imag())-dist(c,m2)*sqrt(2));
}
int main(){
	int t=1;
	scanf("%d",&t);
	while(t--) Solve();
	cerr<<clock()*1.0/CLOCKS_PER_SEC<<'\n';
}