You are given a code:

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

Can you predict the output of `main_solution("sdylrb")` 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": "sdylrb"}, "ref_output": "j_n_a_k_t_s_d_y_l_r_b", "ref_code": "def main_solution(x):\n    return func_13(('jnakt' + x), '_')", "funcname": "main_solution"}
rule