diff --git a/.gitignore b/.gitignore
index b09d2bf9291fa0bc1551b440e3327d70dd3f1430..154f85191803edba06d4f961349f9df05ea80a49 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,6 @@
 # Own:
 *.exe
+.idea
 
 # From https://raw.githubusercontent.com/github/gitignore/master/Haskell.gitignore
 dist
diff --git a/Main.hs b/Main.hs
index 7d4ab60fd4006f2454c00fb6253240316f1f9677..95af32fba1ca1eddda912dce60b56aadcccd5edd 100644
--- a/Main.hs
+++ b/Main.hs
@@ -1,3 +1,3 @@
 import SieveOfEratosthenes
 
-main = putStrLn (show (take 10 (primes) ) )
+main = putStrLn ("First 9 prime numbers: " ++ (show (take 9 (primes) ) ) )
diff --git a/TheSieveOfEratosthenes.md b/TheSieveOfEratosthenes.md
new file mode 100644
index 0000000000000000000000000000000000000000..803e8b1936a8c33315cd761f629a2585f62b182a
--- /dev/null
+++ b/TheSieveOfEratosthenes.md
@@ -0,0 +1,18 @@
+# The Sieve of Eratosthenes
+
+1. Write down the successive "plurals": 2, 3, 4, ...
+2. Repeat:
+    1. Take the first number that is not circled or crossed out.
+    2. Circle it.
+    3. Cross out its proper multiples.
+3. What is left (i.e. the circled numbers) are the successive prime numbers.
+
+**Example**
+
+```
+ 2   3   4   5   6   7   8   9   10   11   12   13   14   15   16   17   18   19   20   21   22   23   24   25 ...
+(2)  3   x   5   x   7   x   9   xx   11   xx   13   xx   15   xx   17   xx   19   xx   21   xx   23   xx   25 ...
+(2) (3)      5       7       x        11        13        xx        17        19        xx        23        25 ...
+(2) (3)     (5)      7                11        13                  17        19                  23        xx ...
+...
+```