Modernize Python 2 code to get ready for Python 3

Project Euler/Problem 01/sol1.py

@@ -4,9 +4,14 @@ If we list all the natural numbers below 10 that are multiples of 3 or 5,
 we get 3,5,6 and 9. The sum of these multiples is 23.
 Find the sum of all the multiples of 3 or 5 below N.
 '''
+from __future__ import print_function
+try:
+    raw_input          # Python 2
+except NameError:
+    raw_input = input  # Python 3
 n = int(raw_input().strip())
-sum=0;
+sum=0
 for a in range(3,n):
     if(a%3==0 or a%5==0):
         sum+=a
-print sum;
+print(sum)