I am having problems iterating over my dictionary. The program should print the average of the numbers beside each name in the dictionary. Can anyone help me figure it out what I'm doing wrong? The following is my current code:

```
guest={"Mary":"15", "Joe":"13", "Dustin":"12"}

def CalcAverage(guest):
    total = 0.0
    numPersons = 0
    for key,value in guest.items():
        numPersons += len(guest[key])
        total = float(sum(guest[value]))
    return total/numPersons

print CalcAverage(guest)

```