You are given a code:

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

Can you predict the output of `main_solution("txdfzcvcfp")` 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": "txdfzcvcfp"}, "ref_output": "t_x_d_f_z_c_v_c_f_p_r_o_t_u_c_i", "ref_code": "def main_solution(x):\n    return func_13((x + 'rotuci'), '_')", "funcname": "main_solution"}
rule