You are given a code:

def main_solution(x):
    return func_13(('ayjm' + x), '-')

Can you predict the output of `main_solution("vygggphk")` 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": "vygggphk"}, "ref_output": "a-y-j-m-v-y-g-g-g-p-h-k", "ref_code": "def main_solution(x):\n    return func_13(('ayjm' + x), '-')", "funcname": "main_solution"}
rule