diff --git a/app/src/main/kotlin/day03/Day03.kt b/app/src/main/kotlin/day03/Day03.kt
new file mode 100644
index 0000000..c073bdd
--- /dev/null
+++ b/app/src/main/kotlin/day03/Day03.kt
@@ -0,0 +1,52 @@
+
+package day03
+
+import kotlin.io.println
+
+class Day03 {
+    fun parse(input: String): String {
+        throw NotImplementedError()
+    }
+
+    fun part1(input: String): Int {
+        val regex = Regex("mul\\((\\d{1,3}),(\\d{1,3})\\)")
+        val muls = regex.findAll(input)
+
+        val product = muls.map { match ->
+            match.groupValues.subList(1, match.groupValues.count())
+            .map { it.toInt() }
+            .toList()
+            .reduce { acc, next -> acc * next }
+        }
+        .toList()
+        .sum()
+
+        return product
+    }
+
+    fun part2(input: String): Int {
+        val regex = Regex("(?:mul\\((\\d{1,3}),(\\d{1,3})\\))|(do(?:n't)?\\(\\))")
+        val muls = regex.findAll(input)
+        var enable = true
+
+        val product = muls.map { match ->
+            var tmp = 0
+            if (match.value == "do()") {
+                enable = true
+            } else if (match.value == "don't()") {
+                enable = false
+            } else if (enable) {
+                tmp = match.groupValues.subList(1, 3)
+                .map { it.toInt() }
+                .toList()
+                .reduce { acc, next -> acc * next }
+            }
+            tmp
+        }
+        .toList()
+        .sum()
+
+        return product
+
+    }
+}
diff --git a/app/src/test/kotlin/day03/Day03Test.kt b/app/src/test/kotlin/day03/Day03Test.kt
new file mode 100644
index 0000000..5b37406
--- /dev/null
+++ b/app/src/test/kotlin/day03/Day03Test.kt
@@ -0,0 +1,42 @@
+
+package day03
+
+import kotlin.test.Test
+import util.InputDownloader
+
+class Day03Test {
+    val dayNum = 3
+    val day = Day03()
+
+    val input = InputDownloader().getInput(dayNum)
+    val example = "xmul(2,4)%&mul[3,7]!@^do_not_mul(5,5)+mul(32,64]then(mul(11,8)mul(8,5))"
+    val example2 = "xmul(2,4)&mul[3,7]!^don't()_mul(5,5)+mul(32,64](mul(11,8)undo()?mul(8,5))"
+
+    @Test fun part1Example() {
+        part1(example, 161)
+    }
+
+    @Test fun part1Solution() {
+        part1(input, 153469856)
+    }
+
+    @Test fun part2Example() {
+        part2(example2, 48)
+    }
+
+    @Test fun part2Solution() {
+        part2(input, 77055967)
+    }
+
+    fun part1(input: String, expected: Int) {
+        val output = day.part1(input)
+        println("output: $output")
+        assert(output == expected)
+    }
+
+    fun part2(input: String, expected: Int) {
+        val output = day.part2(input)
+        println("output: $output")
+        assert(output == expected)
+    }
+}