Added urls

love_letter/love_letter.py

@@ -1,5 +1,7 @@
 #!/usr/bin/python3
 
+# https://www.hackerrank.com/challenges/the-love-letter-mystery
+
 import sys
 
 def char_distance(ca,cb):

service_lane/service_lane.py

@@ -1,5 +1,7 @@
 #!/usr/bin/python3
 
+# https://www.hackerrank.com/challenges/service-lane
+
 import sys
 
 def nextints():

utopian_tree/utopian_tree.py

@@ -1,5 +1,7 @@
 #!/usr/bin/python3
 
+# https://www.hackerrank.com/challenges/utopian-tree
+
 import sys
 
 def calcsize(cycles):