diff --git a/CONTRIBUTORS.md b/CONTRIBUTORS.md
index bbdd8100..9601cf35 100644
--- a/CONTRIBUTORS.md
+++ b/CONTRIBUTORS.md
@@ -183,3 +183,8 @@ Name: [David Chen M.](https://github.com/dchenmei)</br>
 Place: NY, USA</br>
 Coding Experience: C++, Python, Scheme (!) </br>
 Email: lastname#2lastname#1firstname@gmail.com </br>
+
+Name: [Piotr Gajowniczek](https://github.com/piotrgajow)</br>
+Place: Lodz, Poland </br>
+Coding Experience: Groovy, Java, TypeScript, JavaScript, SQL </br>
+Email: piotrgajow@gmail.com </br>
diff --git a/groovy/multiply_ints.groovy b/groovy/multiply_ints.groovy
new file mode 100644
index 00000000..95eee72e
--- /dev/null
+++ b/groovy/multiply_ints.groovy
@@ -0,0 +1 @@
+Closure multiply = { int a, int b -> GroovyCollections.combinations((1..a), (1..b)).size() }