Given a function f continuous in an interval [a,b], and such that f(a) · f(b) < 0, a basic theorem of Mathematics states that there must exist at least one zero of f in (a,b), that is, a real number z such that a < z < b and f(z) = 0.
Given a polynomial p(x) = c4 x4 + c3 x3 + c2 x2 + c1 x + c0 with exactly one zero in (0,1), can you find this zero?
Input
Each input line describes a polynomial p(x) of degree at most 4 with exactly one zero in (0,1). Each polynomial is given in decreasing order of i as follows: c4 4 c3 3 c2 2 c1 1 c0 0. Every ci is a real number. The pairs ci i with ci = 0 are not present in the input.
Output
For every polynomial, print its case number, followed by an approximation of its zero z in (0,1), with the following convention: z must be a real number with exactly 5 digits after the decimal point, such that 0 ≤ z ≤ 0.99999 and p(z) · p(z + 0.00001) < 0. Always print the 5 decimal digits of z.
Observations
Input
-1 2 0.5 0 4 3 -6 1 1 0 4.65 4 -0.11 3 0.53 2 -6.51 1 0.13 0 6.31 4 7.64 3 -5.29 2 0.55 1 -9.2 0
Output
Case 1: zero at 0.70710. Case 2: zero at 0.16993. Case 3: zero at 0.02000. Case 4: zero at 0.99973.