diff --git a/README.md b/README.md
index 139172aa..eb0d9e98 100644
--- a/README.md
+++ b/README.md
@@ -1,8 +1,20 @@
-# solution algorithm problems
+# Contest Kotlin
+
 ![Kotlin](https://img.shields.io/badge/kotlin-%237F52FF.svg?style=for-the-badge&logo=kotlin&logoColor=white)
 ![Android Studio](https://img.shields.io/badge/Android%20Studio-3DDC84.svg?style=for-the-badge&logo=android-studio&logoColor=white)
 
-## Task
+# Description
+
+This repository contains problems of leetcode. We might use this repo how get solution for define
+problem from leetcode. Also We might clone this repo and run or debug problems in android studio.
+
+# How to use
+
+1. Each problem will be in contest module
+2. Each problem have a few solutions. Main solution with using down level code. Alternative Solution
+   with other approaches. Prod Variant - this code might be in prod in application or service. This
+   code using std lib kotlin
+3. For search each problem have kotlin doc with name and number problem. Also each problem have tag
+   for commit for search in github.
+4. Each Topic have package which contains problem
 
-- [leetcode task](app/src/main/java/com/leetcode_kotlin/AlgorithmLeetcode.kt)
-- [codeWars task](app/src/main/java/com/leetcode_kotlin/AlgorithmCodeWars.kt)
diff --git a/contest/src/main/java/com/github/contest/math/MathLeetcode.kt b/contest/src/main/java/com/github/contest/math/MathLeetcode.kt
index e018a27f..1603c1b0 100644
--- a/contest/src/main/java/com/github/contest/math/MathLeetcode.kt
+++ b/contest/src/main/java/com/github/contest/math/MathLeetcode.kt
@@ -191,3 +191,26 @@ fun numberOfPowerfulInt(start: Long, finish: Long, limit: Int, s: String): Long
 
     return if (s.toLong() in start..finish) counter + 1L else counter
 }
+
+/**
+ * 1295. Find Numbers with Even Number of Digits
+ */
+
+val POW = intArrayOf(100_000, 10_000, 1_000, 100, 10, 1)
+
+fun findNumbers(nums: IntArray): Int = nums.filter {
+    isEven(it)
+}.count()
+
+private fun isEven(num: Int): Boolean {
+    var even = true
+
+    for (p in POW) {
+        if (num >= p) break
+        even = !even
+    }
+
+    return even
+}
+
+
diff --git a/contest/src/main/java/com/github/contest/slidingWindow/SlidingWindowLeetcode.kt b/contest/src/main/java/com/github/contest/slidingWindow/SlidingWindowLeetcode.kt
index 915681b5..9a6deacb 100644
--- a/contest/src/main/java/com/github/contest/slidingWindow/SlidingWindowLeetcode.kt
+++ b/contest/src/main/java/com/github/contest/slidingWindow/SlidingWindowLeetcode.kt
@@ -53,4 +53,83 @@ private fun checkUniqueAnswer(store: MutableMap<Char, Int>, cache: MutableMap<Ch
     }
 
     return isUnique
-}
\ No newline at end of file
+}
+
+/**
+ * 3392. Count Subarrays of Length Three With a Condition
+ */
+
+fun countSubArrays(nums: IntArray): Int {
+    var count = 0
+    val k = 3
+    var left = 0
+
+    for (right in nums.indices) {
+        if (right - left == k - 1) {
+            val sum = (nums[left] + nums[right]).toDouble()
+            val middle = nums[left + 1].toDouble() / 2.0
+            if (sum == middle) count++
+            left++
+        }
+    }
+
+    return count
+}
+
+/**
+ * 30. Substring with Concatenation of All Words
+ */
+
+fun findSubstring(s: String, words: Array<String>): List<Int> {
+    val res = mutableListOf<Int>()
+    val totalLen = words[0].length * words.size
+    val wordLen = words[0].length
+    val store = mutableMapOf<String, Int>()
+
+    if (totalLen > s.length) return res
+
+    for (word in words) store[word] = store.getOrDefault(word, 0) + 1
+
+    var left = 0
+
+    for (right in s.indices) {
+        if (right - left == totalLen - 1) {
+            val str = s.substring(left, right + 1)
+            if (isValidWord(str, store, wordLen)) res.add(left)
+            left++
+        }
+    }
+
+    return res
+}
+
+private fun isValidWord(s: String, map: Map<String, Int>, window: Int): Boolean {
+    val seen = mutableMapOf<String, Int>()
+    var left = 0
+
+    for (right in s.indices) {
+        if (right - left == window - 1) {
+            val str = s.substring(left, right + 1)
+            seen[str] = seen.getOrDefault(str, 0) + 1
+            left = right + 1
+        }
+    }
+
+    return when {
+        equalsMap(seen, map) -> true
+        else -> false
+    }
+}
+
+private fun equalsMap(comparable: Map<String, Int>, base: Map<String, Int>): Boolean {
+
+    for ((str, count) in comparable) {
+        if (!base.contains(str)) return false
+        else {
+            val amount = base[str]
+            if (amount != count) return false
+        }
+    }
+
+    return true
+}
diff --git a/contest/src/main/java/com/github/contest/slidingWindow/SlidingWindowProdVariant.kt b/contest/src/main/java/com/github/contest/slidingWindow/SlidingWindowProdVariant.kt
index 0cac09ab..5202631f 100644
--- a/contest/src/main/java/com/github/contest/slidingWindow/SlidingWindowProdVariant.kt
+++ b/contest/src/main/java/com/github/contest/slidingWindow/SlidingWindowProdVariant.kt
@@ -1,5 +1,88 @@
 package com.github.contest.slidingWindow
 
 /**
- *
- */
\ No newline at end of file
+ * 30. Substring with Concatenation of All Words
+ * Prod Variant
+ */
+
+fun findSubstringProdVariant(s: String, words: Array<String>): List<Int> {
+    val res = mutableListOf<Int>()
+    val totalLen = words[0].length * words.size
+    val wordLen = words[0].length
+    val store = mutableMapOf<String, Int>()
+
+    if (totalLen > s.length) return res
+
+    for (word in words) store[word] = store.getOrDefault(word, 0) + 1
+
+    var left = 0
+
+    for (right in s.indices) {
+        if (right - left == totalLen - 1) {
+            val str = s.substring(left, right + 1)
+            if (isValidWord(str, store, wordLen)) res.add(left)
+            left++
+        }
+    }
+
+    return res
+}
+
+private fun isValidWord(s: String, map: Map<String, Int>, window: Int): Boolean {
+    val seen = mutableMapOf<String, Int>()
+
+    s.windowed(window, window) {
+        seen[it.toString()] = seen.getOrDefault(it, 0) + 1
+    }
+
+    return when {
+        equalsMap(seen, map) -> true
+        else -> false
+    }
+}
+
+private fun equalsMap(comparable: Map<String, Int>, base: Map<String, Int>): Boolean {
+
+    for ((str, count) in comparable) {
+        when {
+            !base.contains(str) || base[str] != count -> return false
+            else -> continue
+        }
+    }
+
+    return true
+}
+
+
+/**
+ * Prod Variant with More Kotlin Sugar
+ */
+
+fun findSubstringProdVariantII(s: String, words: Array<String>): List<Int> {
+    val wordLength = words.first().length
+    val totalLength = wordLength * words.size
+
+    if (s.length < totalLength) return listOf()
+
+    val wordCount = words.groupingBy { it }.eachCount()
+
+
+    return (0..s.length - totalLength).filter { start ->
+        val seen = mutableMapOf<String, Int>()
+        words.indices.all { i ->
+            val word = s.substring(start + i * wordLength, start + (i + 1) * wordLength)
+            wordCount.containsKey(word) && seen.merge(word, 1, Int::plus)!! <= wordCount[word]!!
+        }
+    }
+}
+
+/**
+ * 3392. Count Subarrays of Length Three With a Condition
+ * Prod Variant
+ */
+
+fun countSubArraysProdVariant(nums: IntArray): Int =
+    nums.toList().windowed(3).count {
+        (it.first() + it.last()).toDouble() == it[1].toDouble() / 2.0
+    }
+