Given a black-box function `f(x)` which take a value `x` and output `true` for \$p(x)\$, an unknown continious monotone function(not knowing even whether it's increasing), probable; and `false` otherwise. Output an infinite sequence \$a_n\$ such that \$\lim_{n\rightarrow \infty}p(a_n)=0.5\$. You can assume that the result exists.

Reasonable I/O allowed. Shortest code win.

A possible solution:

    for i=1..infty
        S = [i/2] * i*i*2
        for j=0..i*i*2-1
            for k=1..i
                if f(j/i-i)
                    S[j]--
        print minPos([t*t for t in S])/i-i

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