You are given a code:

def main_solution(x):
    return func_20(func_13('bhwcxm', '_'), (x + x))

Can you predict the output of `main_solution("bfrzu")` 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": "bfrzu"}, "ref_output": "bb_fhr_zwu_bcf_rxz_um", "ref_code": "def main_solution(x):\n    return func_20(func_13('bhwcxm', '_'), (x + x))", "funcname": "main_solution"}
rule