You are given a code:

def main_solution(x):
    return func_20(func_15('melrta'), func_1('enth', 3))

Can you predict the output of `main_solution("bbtbo")` 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": "bbtbo"}, "ref_output": "\u00abemn\u00bbt\u00abhee\u00bbn\u00abtlh\u00bbe\u00abnrt\u00bbh\u00abt\u00bb\u00aba\u00bb", "ref_code": "def main_solution(x):\n    return func_20(func_15('melrta'), func_1('enth', 3))", "funcname": "main_solution"}
rule