You are given a code:

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

Can you predict the output of `main_solution("ccz")` 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": "ccz"}, "ref_output": "m_i_l_p_r_m_j", "ref_code": "def main_solution(x):\n    return func_13(('milp' + 'rmj'), '_')", "funcname": "main_solution"}
rule