You are given a code:

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

Can you predict the output of `main_solution("bmunpnqajz")` 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": "bmunpnqajz"}, "ref_output": "b_m_u_n_p_n_q_a_j_zv-l-n", "ref_code": "def main_solution(x):\n    return (func_13(x, '_') + func_13('vln', '-'))", "funcname": "main_solution"}
rule