You are given a code:

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

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