You are given a code:

def main_solution(x):
    return func_20(func_15(x), ('nchwr' + 'jnftcn'))

Can you predict the output of `main_solution("avtas")` 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": "avtas"}, "ref_output": "\u00abnac\u00bbh\u00abwvr\u00bbj\u00abntf\u00bbt\u00abcan\u00bb\u00abs\u00bb", "ref_code": "def main_solution(x):\n    return func_20(func_15(x), ('nchwr' + 'jnftcn'))", "funcname": "main_solution"}
rule