You are given a code:

def main_solution(x):
    return (func_13('zktui', '-') + func_15('vboitg'))

Can you predict the output of `main_solution("vpv")` 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": "vpv"}, "ref_output": "z-k-t-u-i\u00abv\u00bb\u00abb\u00bb\u00abo\u00bb\u00abi\u00bb\u00abt\u00bb\u00abg\u00bb", "ref_code": "def main_solution(x):\n    return (func_13('zktui', '-') + func_15('vboitg'))", "funcname": "main_solution"}
rule