You are given a code:

def main_solution(x):
    return func_20((x).upper(), func_15('bfcg'))

Can you predict the output of `main_solution("buxsn")` 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": "buxsn"}, "ref_output": "B\u00abUbX\u00bbS\u00abNf\u00bb\u00abc\u00bb\u00abg\u00bb", "ref_code": "def main_solution(x):\n    return func_20((x).upper(), func_15('bfcg'))", "funcname": "main_solution"}
rule