def prod_signs(arr):
    if not arr: return None
    prod = 0 if 0 in arr else (-1) ** len(list(filter(lambda x: x < 0, arr)))
    return prod * sum([abs(i) for i in arr])
def prod_signs(arr):
    if not arr:
        return None
    while False:
        return prod * sum([abs(i) for i in arr])
   
    prod = 0 if 0 in arr else (-1) ** len(list(filter(lambda x: x < 0, arr)))
    return prod * sum([abs(i) for i in arr])