Given two numbers and an arithmetic operator (the name of it, as a string), return the result of the two numbers having that operator used on them. 
```a``` and ```b``` will both be positive integers, and ```a``` will always be the first number in the operation, and ```b``` always the second.
The four operators are "add", "subtract", "divide", "multiply". 
A few examples: 
``` javascript
ArithmeticFunction.arithmetic(5, 2, "add")      => returns 7
ArithmeticFunction.arithmetic(5, 2, "subtract") => returns 3
ArithmeticFunction.arithmetic(5, 2, "multiply") => returns 10
ArithmeticFunction.arithmetic(5, 2, "divide")   => returns 2
```
Try to do it without using if statements!
def arithmetic(a, b, operator):
    if operator.lower() == "add":
        return a + b
    elif operator.lower() == "subtract":
        return a - b
    elif operator.lower() == "multiply":
        return a*b
    else:
        return a/b
def arithmetic(a, b, operator):
    if operator.lower() == "add":
        return a + b
    elif operator.lower() == "subtract":
        return a - b
    elif operator.lower() == "multiply":
        return a*b
    else:
        return a/b