You are given a code:

def main_solution(x):
    return func_20('qqgs', 'fyfxc')

Can you predict the output of `main_solution("yvbyyumk")` 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": "yvbyyumk"}, "ref_output": "qfqygfsxc", "ref_code": "def main_solution(x):\n    return func_20('qqgs', 'fyfxc')", "funcname": "main_solution"}
rule