correcting errors found by students

subjects/flags/README.md

@@ -24,25 +24,25 @@ $ go run . --order 43a21
 $ go run .
 --insert
   -i
-    This flag inserts the string into the string passed as argument.
+         This flag inserts the string into the string passed as argument.
 --order
   -o
-    This flag will behave like a boolean, if it is called it will order the argument.
+         This flag will behave like a boolean, if it is called it will order the argument.
 $
 $ go run . -h
 --insert
   -i
-    This flag inserts the string into the string passed as argument.
+         This flag inserts the string into the string passed as argument.
 --order
   -o
-    This flag will behave like a boolean, if it is called it will order the argument.
+         This flag will behave like a boolean, if it is called it will order the argument.
 $
 $ go run . --help
 --insert
   -i
-    This flag inserts the string into the string passed as argument.
+         This flag inserts the string into the string passed as argument.
 --order
   -o
-    This flag will behave like a boolean, if it is called it will order the argument.
+         This flag will behave like a boolean, if it is called it will order the argument.
 $
 ```

subjects/nrune/README.md

@@ -2,7 +2,7 @@
 
 ### Instructions
 
-Write a function that returns the nth `rune` of a `string`. If not possible, it returns `0`.
+Write a function that returns the nth `rune` of a `string`. If it's not possible it doesn't return anything.
 
 ### Expected function
 

subjects/printstr/README.md

@@ -30,7 +30,7 @@ And its output :
 
 ```console
 $ go run . | cat -e
-Hello World!%
+Hello World!$
 $
 ```