diff --git a/src/main/kotlin/p30xx/Problem3019.kt b/src/main/kotlin/p30xx/Problem3019.kt
new file mode 100644
index 00000000..534e4d0a
--- /dev/null
+++ b/src/main/kotlin/p30xx/Problem3019.kt
@@ -0,0 +1,21 @@
+package p30xx
+
+import util.expect
+
+fun main() {
+    class Solution {
+        fun countKeyChanges(s: String): Int {
+            val set = setOf(0, 'A' - 'a', 'a' - 'A')
+
+            return (1 until s.length).count {
+                s[it] - s[it - 1] !in set
+            }
+        }
+    }
+
+    expect {
+        Solution().countKeyChanges(
+            ""
+        )
+    }
+}