"If it is not possible to construct the fence from the specified blocks, write 0.00." - dementia

binary search from the maximum side across the floors to infinity is a bad idea - a ternary search is better suited, it can be run over all segments equal in length to the root from infinity, and also for prevention it is worth adding a few additional random segments (about 10,000)
I would highlight a few good infinities such as 5e6, 1e8, 1e10, 1e6, 1e5, 2.625e6

The order of the walls is not important

#define ld long double

ld arcsin(ld k) {
    if (k >= 1) {
        k = 1;
    }
    if (k <= -1) {
        k = -1;
    }

    return asinl(k);
}
(I hope you won't need this feature.)

i think 1e-10 nice eps, but i dont sure