You are given a code:

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

Can you predict the output of `main_solution("imbv")` 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": "imbv"}, "ref_output": "n\u00abrip\u00bbf\u00abgme\u00bbc\u00abvbj\u00bbz\u00abv\u00bb", "ref_code": "def main_solution(x):\n    return func_20(('nrpfge' + 'cvjz'), func_15(x))", "funcname": "main_solution"}
rule