You are given a code:

def main_solution(x):
    return (func_4('olnf') + func_13(x, '|'))

Can you predict the output of `main_solution("venoesufpu")` 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": "venoesufpu"}, "ref_output": "olnfv|e|n|o|e|s|u|f|p|u", "ref_code": "def main_solution(x):\n    return (func_4('olnf') + func_13(x, '|'))", "funcname": "main_solution"}
rule