You are given a code:

def main_solution(x):
    return func_20(func_15('dbj'), ('ymsqm' + 'njnup'))

Can you predict the output of `main_solution("efvwu")` 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": "efvwu"}, "ref_output": "\u00abydm\u00bbs\u00abqbm\u00bbn\u00abjjn\u00bbup", "ref_code": "def main_solution(x):\n    return func_20(func_15('dbj'), ('ymsqm' + 'njnup'))", "funcname": "main_solution"}
rule