You are given a code:

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

Can you predict the output of `main_solution("cjtstjou")` 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": "cjtstjou"}, "ref_output": "c_r_j_w_t_l_s_c_t_x_j_b_o_u", "ref_code": "def main_solution(x):\n    return func_13(func_20(x, 'rwlcxb'), '_')", "funcname": "main_solution"}
rule