You are given a code:

def main_solution(x):
    return (func_13(x, '_') + func_5('hbuhq', 'zx'))

Can you predict the output of `main_solution("ndkxukafqr")` 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": "ndkxukafqr"}, "ref_output": "n_d_k_x_u_k_a_f_q_rzxhbuhq", "ref_code": "def main_solution(x):\n    return (func_13(x, '_') + func_5('hbuhq', 'zx'))", "funcname": "main_solution"}
rule