This is a simple mathematics problem

The question is simple, first give you a function like , and give you a point (a, b,J(a,b)) in this function. Can you calculate the distance of the point along the surface to the origin (0,0,0)? 

给一个椭圆抛物面让你求抛物面上的点沿抛物面到原点的距离

There multiple test cases in the input

for each test case contain one line

The line have four integer A, B, a, b mentioned above

0<A,B<100, -100<a,b<100 

For each test case output a number means the distance, error precision less than 1e-6.

1 1 1 1
2 2 2 2

3.285772
45.460735