1237. Find Positive Integer Solution for a Given Equation

Given a callable function f(x, y) with a hidden formula and a value z, reverse engineer the formula and return all positive integer pairs x and y where f(x,y) == z. You may return the pairs in any order. While the exact formula is hidden, the function is monotonically increasing, i.e.: - f(x, y) < f(x + 1, y) - f(x, y) < f(x, y + 1) The function interface is defined like this: interface Custo