You are given a code:

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

Can you predict the output of `main_solution("flb")` 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": "flb"}, "ref_output": "v\u00abkfq\u00bbv\u00abqlz\u00bbf\u00ablbb\u00bb", "ref_code": "def main_solution(x):\n    return func_20(('vkqvqz' + x), func_15(x))", "funcname": "main_solution"}
rule