You are given a code:

def main_solution(x):
    return func_20(func_13(x, '_'), func_5(x, 'wf'))

Can you predict the output of `main_solution("mjvilltwpt")` 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": "mjvilltwpt"}, "ref_output": "mw_fjm_jvv_iil_llt_wlp_tt_w_p_t", "ref_code": "def main_solution(x):\n    return func_20(func_13(x, '_'), func_5(x, 'wf'))", "funcname": "main_solution"}
rule