Simplify if function

I want to simplify the formula in column E, for small samples it is easy but I need to use it for a really large sample.
The formula is a if function
The formula: look first if the formula above the cell is a zero if this is not the case, look if the cell above that cell is a zero, if that is not the case look if the cell above that cell is a zero and so on. If the value in the cell is an one the answer is the cell right of it.

I have attached a example, the idea is really simple, if you look at the formula in cell b9 you get the idea

I hope someone can help me.

Thanks!