Given is the function f(x) = 2^{30.403243784-x2} 10^-9 ( is the floor-function),
the sequence u_n is defined by u₀ = -1 and u_n+1 = f(u_n).

Find u_n + u_n+1 for n = 10¹².
Give your answer with 9 digits after the decimal point.