You are given a code:

def main_solution(x):
    return func_13(func_20('mfo', 'ktkpyk'), '_')

Can you predict the output of `main_solution("exqtq")` 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": "exqtq"}, "ref_output": "m_k_f_t_o_k_p_y_k", "ref_code": "def main_solution(x):\n    return func_13(func_20('mfo', 'ktkpyk'), '_')", "funcname": "main_solution"}
rule