ll@t;
rep(t){
	ll@n;
	double@x,@h[n],@a[n];
	double z=1e99;
	rrep(i,1,n){
		h[i]-=h[i-1];
	}
	rep(i,n){
		double w=0,p=0;
		rep(j,i){
			if(a[i]>=a[j]){
				break_continue;
			}
			double r=a[i]/a[j];
			double t=r/sqrt(1-r*r);
			p+=t*h[j];
			w+=hypot(t,1)*h[j]*a[j];
		}
		if(x/2-p<0) continue;
		w+=(x/2-p)*a[i];
		z<?=w;
	}
	wt(2z);
}