Modernize Python 2 code to get ready for Python 3

Project Euler/Problem 01/sol3.py

@@ -7,6 +7,11 @@ Find the sum of all the multiples of 3 or 5 below N.
 '''
 This solution is based on the pattern that the successive numbers in the series follow: 0+3,+2,+1,+3,+1,+2,+3.
 '''
+from __future__ import print_function
+try:
+    raw_input          # Python 2
+except NameError:
+    raw_input = input  # Python 3
 n = int(raw_input().strip())
 sum=0;
 num=0;
@@ -39,4 +44,4 @@ while(1):
     if(num>=n):
         break
     sum+=num
-print sum;
+print(sum);