You are given a code:

def main_solution(x):
    return func_5(func_13(x, '_'), 'jog')

Can you predict the output of `main_solution("buunutgtw")` 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": "buunutgtw"}, "ref_output": "jogb_u_u_n_u_t_g_t_w", "ref_code": "def main_solution(x):\n    return func_5(func_13(x, '_'), 'jog')", "funcname": "main_solution"}
rule