How to consume command line arguments using raw_input() instead of sys.argv

I am new to python I have developed the following code for some online coding submission. Now my problem is this coding site is not accepting sys.argv. How do I convert this code to take raw_input from command line. raw_input is confusing as compared to sys.argv. Please help. Thanks in advance.

import sys
 ln = int(sys.argv[1])
 #create list of elements which are sum of two command line input
 list = []
 i = 2
 while i <= ln:
     sum = int(sys.argv[i]) + int(sys.argv[i+1])
     list.append(sum)
     i = i + 2
 #update list with elements which are sum of the two elements within the list    
 j = 0
 while j < len(list) - 1:
     list.append(list[j]+list[j+1])
     j = j + 2
 #get final sum using addition of all the elements in the list
 k = 0
 sum = 0
 while k < len(list):
     sum =  sum + list[k]
     k = k + 1
 print sum
 

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