diff --git a/src/Test80.kt b/src/Test80.kt
new file mode 100644
index 0000000..2fdc074
--- /dev/null
+++ b/src/Test80.kt
@@ -0,0 +1,23 @@
+class Test80 {
+    class Solution {
+        fun removeDuplicates(nums: IntArray): Int {
+            if (nums.size <= 2){
+                return nums.size
+            }
+
+            var slow = 1
+
+            for (fast in 2.. nums.lastIndex){
+                if (nums[fast] != nums[slow] || nums[slow] != nums[slow-1]) {
+                    nums[++slow] = nums[fast]
+                }
+            }
+            return slow +1
+        }
+    }
+
+    fun test(){
+        println(Solution().removeDuplicates(intArrayOf(0,0,1,1,1,1,2,3,3)))
+    }
+
+}
\ No newline at end of file