You are given a code:

def main_solution(x):
    return func_17(func_4('fgvtri'))

Can you predict the output of `main_solution("fllsxrw")` 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": "fllsxrw"}, "ref_output": "irtvgf", "ref_code": "def main_solution(x):\n    return func_17(func_4('fgvtri'))", "funcname": "main_solution"}
rule