You are given a code:

def main_solution(x):
    return func_20(func_15(x), func_20('nxotp', 'agm'))

Can you predict the output of `main_solution("vstkmviwkj")` 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": "vstkmviwkj"}, "ref_output": "\u00abnva\u00bbx\u00abgso\u00bbm\u00abttp\u00bb\u00abk\u00bb\u00abm\u00bb\u00abv\u00bb\u00abi\u00bb\u00abw\u00bb\u00abk\u00bb\u00abj\u00bb", "ref_code": "def main_solution(x):\n    return func_20(func_15(x), func_20('nxotp', 'agm'))", "funcname": "main_solution"}
rule