You are given a code:

def main_solution(x):
    return func_20(func_13(x, '-'), func_15('bfl'))

Can you predict the output of `main_solution("gvvnagaz")` 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": "gvvnagaz"}, "ref_output": "g\u00ab-bv\u00bb-\u00abvf-\u00bbn\u00ab-la\u00bb-g-a-z", "ref_code": "def main_solution(x):\n    return func_20(func_13(x, '-'), func_15('bfl'))", "funcname": "main_solution"}
rule