You are given a code:

def main_solution(x):
    return func_20(func_15('mruj'), func_20('gsjpva', x))

Can you predict the output of `main_solution("nbka")` 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": "nbka"}, "ref_output": "\u00abgmn\u00bbs\u00abbrj\u00bbk\u00abpua\u00bbv\u00abaj\u00bb", "ref_code": "def main_solution(x):\n    return func_20(func_15('mruj'), func_20('gsjpva', x))", "funcname": "main_solution"}
rule