You are given a code:

def main_solution(x):
    return func_20(('umpvs' + 'fzbu'), func_4('vdoil'))

Can you predict the output of `main_solution("ncp")` 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": "ncp"}, "ref_output": "uvmdpovislfzbu", "ref_code": "def main_solution(x):\n    return func_20(('umpvs' + 'fzbu'), func_4('vdoil'))", "funcname": "main_solution"}
rule