Collections.namedtuple()

_{collections.namedtuple()}

Basically, namedtuples are easy to create, lightweight object types.
They turn tuples into convenient containers for simple tasks.
With namedtuples, you don’t have to use integer indices for accessing members of a tuple.

Example

_{Code 01}

>>> from collections import namedtuple
>>> Point = namedtuple('Point','x,y')
>>> pt1 = Point(1,2)
>>> pt2 = Point(3,4)
>>> dot_product = ( pt1.x * pt2.x ) +( pt1.y * pt2.y )
>>> print dot_product
11

_{Code 02}

>>> from collections import namedtuple
>>> Car = namedtuple('Car','Price Mileage Colour Class')
>>> xyz = Car(Price = 100000, Mileage = 30, Colour = 'Cyan', Class = 'Y')
>>> print xyz
Car(Price=100000, Mileage=30, Colour='Cyan', Class='Y')
>>> print xyz.Class
Y

Task

Dr. John Wesley has a spreadsheet containing a list of student's , , and .

Your task is to help Dr. Wesley calculate the average marks of the students.

_{Note:

1. Columns can be in any order. IDs, marks, class and name can be written in any order in the spreadsheet.

2. Column names are ID, MARKS, CLASS and NAME. (The spelling and case type of these names won't change.)}

Input Format

The first line contains an integer , the total number of students.
The second line contains the names of the columns in any order.
The next lines contains the , , and , under their respective column names.

Constraints

Output Format

Print the average marks of the list corrected to 2 decimal places.

Sample Input

_{TESTCASE 01}

5
ID         MARKS      NAME       CLASS     
1          97         Raymond    7         
2          50         Steven     4         
3          91         Adrian     9         
4          72         Stewart    5         
5          80         Peter      6

_{TESTCASE 02}

5
MARKS      CLASS      NAME       ID        
92         2          Calum      1         
82         5          Scott      2         
94         2          Jason      3         
55         8          Glenn      4         
82         2          Fergus     5

Sample Output

_{TESTCASE 01}

78.00

_{TESTCASE 02}

81.00

Explanation

_{TESTCASE 01}

Average =

Can you solve this challenge in 4 lines of code or less?
NOTE: There is no penalty for solutions that are correct but have more than 4 lines.