You are given a code:

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

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