You are given a code:

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

Can you predict the output of `main_solution("tietzi")` 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": "tietzi"}, "ref_output": "u-m-dw-o-y-k-b", "ref_code": "def main_solution(x):\n    return (func_13('umd', '-') + func_13('woykb', '-'))", "funcname": "main_solution"}
rule