You are given a code:

def main_solution(x):
    return (func_3('hvvcr') + func_13('lccnan', '-'))

Can you predict the output of `main_solution("mmnbu")` 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": "mmnbu"}, "ref_output": "chrvvl-c-c-n-a-n", "ref_code": "def main_solution(x):\n    return (func_3('hvvcr') + func_13('lccnan', '-'))", "funcname": "main_solution"}
rule