You are given a code:

def main_solution(x):
    return func_13(('xjzh' + 'ytnfew'), '|')

Can you predict the output of `main_solution("gkbumyncf")` 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": "gkbumyncf"}, "ref_output": "x|j|z|h|y|t|n|f|e|w", "ref_code": "def main_solution(x):\n    return func_13(('xjzh' + 'ytnfew'), '|')", "funcname": "main_solution"}
rule