def bsearch(array, target)
    min = 0
    max = array.length - 1
    while max >= min
        mid = (min + max).div(2)
        if target == array[mid]
            return mid
        end        
        if target > array[mid]
            min = mid + 1
        else
            max = mid - 1
        end
    end
    return -1
end

puts bsearch([1,2,3,4,5], 1)