You are given a code:

def main_solution(x):
    return func_13(func_19('csrxrk', 2), '-')

Can you predict the output of `main_solution("fnvb")` 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": "fnvb"}, "ref_output": "r-x-r-k-c-s", "ref_code": "def main_solution(x):\n    return func_13(func_19('csrxrk', 2), '-')", "funcname": "main_solution"}
rule