diff --git a/euclidian_greatest_divisor.c b/euclidian_greatest_divisor.c
new file mode 100644
index 0000000..e7014bb
--- /dev/null
+++ b/euclidian_greatest_divisor.c
@@ -0,0 +1,5 @@
+#define mod %
+
+int euclidian_gcd(int a, int b) {
+    return b ? euclidian_gcd(b, a mod b) : a;
+}