You are given a code:

def main_solution(x):
    return func_20(func_13('flvj', '_'), func_15('flhmax'))

Can you predict the output of `main_solution("ugflljzgmv")` 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": "ugflljzgmv"}, "ref_output": "f\u00ab_fl\u00bb_\u00abvl_\u00bbj\u00abh\u00bb\u00abm\u00bb\u00aba\u00bb\u00abx\u00bb", "ref_code": "def main_solution(x):\n    return func_20(func_13('flvj', '_'), func_15('flhmax'))", "funcname": "main_solution"}
rule