You are given a code:

def main_solution(x):
    return (func_15(x) + func_13('gfvkb', '_'))

Can you predict the output of `main_solution("nkdrae")` 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": "nkdrae"}, "ref_output": "\u00abn\u00bb\u00abk\u00bb\u00abd\u00bb\u00abr\u00bb\u00aba\u00bb\u00abe\u00bbg_f_v_k_b", "ref_code": "def main_solution(x):\n    return (func_15(x) + func_13('gfvkb', '_'))", "funcname": "main_solution"}
rule