You are given a code:

def main_solution(x):
    return func_20(func_20('yfopxt', x), func_15(x))

Can you predict the output of `main_solution("njj")` 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": "njj"}, "ref_output": "y\u00abnnf\u00bbj\u00abojj\u00bbp\u00abxjt\u00bb", "ref_code": "def main_solution(x):\n    return func_20(func_20('yfopxt', x), func_15(x))", "funcname": "main_solution"}
rule