You are given a code:

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

Can you predict the output of `main_solution("fmvj")` 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": "fmvj"}, "ref_output": "f-m-v-j-e-e-x-y-n-v", "ref_code": "def main_solution(x):\n    return func_13((x + 'eexynv'), '-')", "funcname": "main_solution"}
rule