Update nruneprog.en.md

subjects/nruneprog.en.md

@@ -1,4 +1,15 @@
-## nrune
+## nruneprog
+
+##**WARNING! VERY IMPORTANT!**
+
+For this exercise a function will be tested **with the exam own main**. However the student **still needs** to submit a structured program:
+
+This means that:
+
+- The package needs to be named `package main`.
+- The submitted code needs one declared function main(```func main()```) even if empty.
+- The function main declared needs to **also pass** the `Restrictions Checker`(illegal functions tester). It is advised for the student to just empty the function main after its own testings are done.
+- Every other rules are obviously the same than for a `program`.
 
 ### Instructions
 
@@ -11,7 +22,3 @@ func NRune(s string, n int) rune {
 
 }
 ```
-
-### Note
-
-Remember to submit a main function testing the function