You are given a code:

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

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