You are given a code:

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

Can you predict the output of `main_solution("feifpbivo")` 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": "feifpbivo"}, "ref_output": "mffk_p_r_d", "ref_code": "def main_solution(x):\n    return func_5(func_13('kprd', '_'), 'mff')", "funcname": "main_solution"}
rule