You are given a code:

def main_solution(x):
    return func_20(func_4('nvrjvv'), func_13('lrellf', '-'))

Can you predict the output of `main_solution("onwfb")` 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": "onwfb"}, "ref_output": "nlv-rrj-vev-l-l-f", "ref_code": "def main_solution(x):\n    return func_20(func_4('nvrjvv'), func_13('lrellf', '-'))", "funcname": "main_solution"}
rule