You are given a code:

def main_solution(x):
    return func_13(('avkee' + 'uijt'), '_')

Can you predict the output of `main_solution("ztuucgxx")` 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": "ztuucgxx"}, "ref_output": "a_v_k_e_e_u_i_j_t", "ref_code": "def main_solution(x):\n    return func_13(('avkee' + 'uijt'), '_')", "funcname": "main_solution"}
rule