You are given a code:

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

Can you predict the output of `main_solution("mxjtnkz")` 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": "mxjtnkz"}, "ref_output": "\u00abymd\u00bby\u00abgxm\u00bbx\u00abjjt\u00bbn\u00abktz\u00bb\u00abn\u00bb\u00abk\u00bb\u00abz\u00bb", "ref_code": "def main_solution(x):\n    return func_20(func_15(x), ('ydyg' + x))", "funcname": "main_solution"}
rule