You are given a code:

def main_solution(x):
    return (func_5(x, 'rbtv') + func_13('ofudvt', '-'))

Can you predict the output of `main_solution("mpnjzkph")` 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": "mpnjzkph"}, "ref_output": "rbtvmpnjzkpho-f-u-d-v-t", "ref_code": "def main_solution(x):\n    return (func_5(x, 'rbtv') + func_13('ofudvt', '-'))", "funcname": "main_solution"}
rule