You are given a code:

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

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