You are given a code:

def main_solution(x):
    return func_20('bup', x)

Can you predict the output of `main_solution("tippbafut")` 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": "tippbafut"}, "ref_output": "btuipppbafut", "ref_code": "def main_solution(x):\n    return func_20('bup', x)", "funcname": "main_solution"}
rule