You are given a code:

def main_solution(x):
    return (func_22('sfwu') + func_13('oow', '-'))

Can you predict the output of `main_solution("vthnxkzaa")` 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": "vthnxkzaa"}, "ref_output": "sfwuo-o-w", "ref_code": "def main_solution(x):\n    return (func_22('sfwu') + func_13('oow', '-'))", "funcname": "main_solution"}
rule