def average_grade(adict):

"""

Returns the average grade among all students.

 

The dictionary adict has netids for keys and numbers 0-100 for values.

These represent the grades that the students got on the exam. This function

averages those grades and returns a value.

 

Examples:

average_grade({'wmw2' : 55, 'abc3' : 90, 'jms45': 86}) returns (55+90+86)/3 = 77

average_grade({'wmw2' : 55}) returns 55

average_grade({}) returns 0

 

Parameter adict: the dictionary of grades

Precondition: adict is dictionary mapping strings to ints

"""