You are given a code:

def main_solution(x):
    return ('pkc' + 'kir')

Can you predict the output of `main_solution("vbwiiyn")` 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": "vbwiiyn"}, "ref_output": "pkckir", "ref_code": "def main_solution(x):\n    return ('pkc' + 'kir')", "funcname": "main_solution"}
rule