Python3 代码

x = eval(input())
if x <= 2000:
    print("Isento")
elif x <= 3000:
    print("R$",f'{(x-2000)*(8/100):.2f}')
elif x <= 4500:
    print("R$",f'{(x-3000)*(18/100)+1000*(8/100):.2f}')
else:
    print("R$",f'{(x-4500)*(28/100)+1000*(8/100)+1500*(18/100):.2f}')