You are given a code:

def main_solution(x):
    return func_20(func_13(x, '-'), (x + 'zhbube'))

Can you predict the output of `main_solution("kgfsmmlpum")` without writing any code? Please reason and put your final answer in the following json format: {"output": <your output>}, where <your output> should be the final string.
user
{"ref_input": {"x": "kgfsmmlpum"}, "ref_output": "kk-ggf-sfm-msl-pmu-mmz-hlb-upb-eu-m", "ref_code": "def main_solution(x):\n    return func_20(func_13(x, '-'), (x + 'zhbube'))", "funcname": "main_solution"}
rule