You are given a code:

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

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