You are given a code:

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

Can you predict the output of `main_solution("rfdufmtvpe")` 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": "rfdufmtvpe"}, "ref_output": "r\u00abfrd\u00bbu\u00abffm\u00bbt\u00abvdp\u00bbe\u00abiub\u00bbp\u00abrfm\u00bbm\u00abm\u00bb\u00abt\u00bb\u00abv\u00bb\u00abp\u00bb\u00abe\u00bb", "ref_code": "def main_solution(x):\n    return func_20((x + 'ibprmm'), func_15(x))", "funcname": "main_solution"}
rule