You are given a code:

def main_solution(x):
    return ('dujyeb' + 'ntdvdw')

Can you predict the output of `main_solution("nnbl")` 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": "nnbl"}, "ref_output": "dujyebntdvdw", "ref_code": "def main_solution(x):\n    return ('dujyeb' + 'ntdvdw')", "funcname": "main_solution"}
rule