You are given a code:

def main_solution(x):
    return ('apj' + 'tce')

Can you predict the output of `main_solution("qkj")` 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": "qkj"}, "ref_output": "apjtce", "ref_code": "def main_solution(x):\n    return ('apj' + 'tce')", "funcname": "main_solution"}
rule