You are given a code:

def main_solution(x):
    return (func_15(x) + func_4('pbt'))

Can you predict the output of `main_solution("iifvvcztg")` 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": "iifvvcztg"}, "ref_output": "\u00abi\u00bb\u00abi\u00bb\u00abf\u00bb\u00abv\u00bb\u00abv\u00bb\u00abc\u00bb\u00abz\u00bb\u00abt\u00bb\u00abg\u00bbpbt", "ref_code": "def main_solution(x):\n    return (func_15(x) + func_4('pbt'))", "funcname": "main_solution"}
rule