diff --git a/2015/src/day04.clj b/2015/src/day04.clj
new file mode 100644
index 0000000..35835b1
--- /dev/null
+++ b/2015/src/day04.clj
@@ -0,0 +1,21 @@
+(ns day04
+  (:require [input-manager]
+            [clojure.set])
+  (:import java.security.MessageDigest java.math.BigInteger))
+
+(def input (input-manager/get-input-raw 2015 4))
+
+(defn string->md5 [s]
+  (let [algorithm (MessageDigest/getInstance "MD5")
+        raw (.digest algorithm (.getBytes s))]
+    (format "%032x" (BigInteger. 1 raw))))
+
+(defn solution [target-prefix]
+  (loop [i 0]
+    (let [md5 (string->md5 (str input i))]
+      (if (.startsWith md5 target-prefix)
+        i
+        (recur (inc i))))))
+
+(solution "00000")
+(solution "000000")