ref #16 better processing of the last-block argument

+sample with national-characters vars

docs/tutorial.md

@@ -15,8 +15,7 @@ __Other documents to read__ maybe after this one:
 - [OOP notes](OOP.md)
 - [math in Lyng](math.md)
 - Some class references: [List], [Real], [Range], [Iterable], [Iterator]
-- Some samples: [combinatorics](samples/combinatorics.lyng.md)
-    See [samples folder](samples)
+- Some samples: [combinatorics](samples/combinatorics.lyng.md), national vars and loops: [сумма ряда](samples/сумма_ряда.lyng.md). More at [samples folder](samples)
 
 # Expressions