You are given a code:

def main_solution(x):
    return func_13(func_20('bta', 'zcv'), '_')

Can you predict the output of `main_solution("uaty")` 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": "uaty"}, "ref_output": "b_z_t_c_a_v", "ref_code": "def main_solution(x):\n    return func_13(func_20('bta', 'zcv'), '_')", "funcname": "main_solution"}
rule