diff --git a/README.md b/README.md
index e40c1f1..2cb95bb 100755
--- a/README.md
+++ b/README.md
@@ -27,10 +27,13 @@
 9. [Longest Common Prefix](https://github.com/karpovigorok/leetcode/blob/master/src/LongestCommonPrefix/Solution.php)
 10. [Count Primes](https://github.com/karpovigorok/leetcode/blob/master/src/CountPrimes/Solution.php)
 11. [Rotate Array](https://github.com/karpovigorok/leetcode/blob/master/src/RotateArray/Solution.php)
-12.	[Sqrt(x)](https://github.com/karpovigorok/leetcode/blob/master/src/Sqrtx/Solution.php)
+12. [Sqrt(x)](https://github.com/karpovigorok/leetcode/blob/master/src/Sqrtx/Solution.php)
 13. [Sum of Two Integers](https://github.com/karpovigorok/leetcode/blob/master/src/SumOfTwoIntegers/Solution.php)
 14. [Valid Parentheses](https://github.com/karpovigorok/leetcode/blob/master/src/ValidParentheses/Solution.php)
 15. [Implement strStr()](https://github.com/karpovigorok/leetcode/blob/master/src/ImplementStrstr/Solution.php)
 16. [Merge Sorted Array](https://github.com/karpovigorok/leetcode/blob/master/src/MergeSortedArray/Solution.php)
 17. [Remove Duplicates from Sorted Array](https://github.com/karpovigorok/leetcode/blob/master/src/RemoveDuplicatesFromSortedArray/Solution.php)
-18. [Min Stack](https://github.com/karpovigorok/leetcode/blob/master/result/min-stack.php)
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+18. [Min Stack](https://github.com/karpovigorok/leetcode/blob/master/result/min-stack.php)
+19. [Merge Two Sorted Lists](https://github.com/karpovigorok/leetcode/blob/master/src/MergeTwoSortedLists/Solution.php)
+20. [Search Insert Position](https://github.com/karpovigorok/leetcode/blob/master/src/SearchInsertPosition/Solution.php)
+21. [First Bad Version](https://github.com/karpovigorok/leetcode/blob/master/src/FirstBadVersion/Solution.php)
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diff --git a/result/first-bad-version.php b/result/first-bad-version.php
new file mode 100644
index 0000000..9edf0b0
--- /dev/null
+++ b/result/first-bad-version.php
@@ -0,0 +1,8 @@
+<?php
+
+require "../vendor/autoload.php";
+
+use Leetcode\FirstBadVersion\Solution;
+
+$solution = new Solution();
+echo $solution->firstBadVersion(2);
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diff --git a/result/search-insert-position.php b/result/search-insert-position.php
new file mode 100644
index 0000000..6336fe0
--- /dev/null
+++ b/result/search-insert-position.php
@@ -0,0 +1,10 @@
+<?php
+require "../vendor/autoload.php";
+
+use Leetcode\SearchInsertPosition\Solution;
+
+$solution = new Solution();
+
+$nums = [-1];
+$target = 0;
+print $solution->searchInsert($nums, $target);
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diff --git a/src/FirstBadVersion/Solution.php b/src/FirstBadVersion/Solution.php
new file mode 100644
index 0000000..e39930f
--- /dev/null
+++ b/src/FirstBadVersion/Solution.php
@@ -0,0 +1,93 @@
+<?php
+
+namespace Leetcode\FirstBadVersion;
+
+/**
+ * Project: leetcode
+ * Problem URL: https://leetcode.com/problems/first-bad-version/
+ * Difficulty: Easy
+ * Description: You are a product manager and currently leading a team to develop a new product. Unfortunately, the latest version of your product fails the quality check. Since each version is developed based on the previous version, all the versions after a bad version are also bad.
+ * Suppose you have n versions [1, 2, ..., n] and you want to find out the first bad one, which causes all the following ones to be bad.
+ * You are given an API bool isBadVersion(version) which returns whether version is bad. Implement a function to find the first bad version. You should minimize the number of calls to the API.
+ *
+ * Author: Igor Karpov <igorok.karpov@gmail.com>
+ * Date: 1/8/2020
+ * Time: 6:07 PM
+ * Class Solution
+
+
+
+
+/* The isBadVersion API is defined in the parent class VersionControl.
+      public function isBadVersion($version){} */
+
+class VersionControl {
+    private $_bad_version = 2;
+    public function isBadVersion($version): bool
+    {
+        //print $version . " is " . intval($this->_bad_version <= $version) . PHP_EOL;
+        return ($this->_bad_version <= $version);
+    }
+}
+
+class Solution extends VersionControl {
+    /**
+     * @param Integer $n
+     * @return Integer
+     */
+    private $_right = 0;
+
+    public function firstBadVersion($n): int {
+        $start = 1;
+        if($n <= 1) {
+            return $n;
+        }
+        $end = $n;
+        while($start < $end) {
+            $position2check = intdiv(($start + $end), 2 );
+            if($this->isBadVersion($position2check)) {
+                if($position2check == 1) return 1;
+                if($end - $start == 1) return $end;
+                $end = $position2check;
+            }
+            else {
+                if($start == $position2check) {
+                    $start = $end;
+                }
+                else {
+                    $start = $position2check;
+                }
+            }
+        }
+        return $end;
+    }
+
+    public function firstBadVersionWithRecurtion($n): int
+    {
+        if($this->_right == 0) {
+            $this->_right = $n;
+        }
+        if($n <= 0) {
+            return $n;
+        }
+        if($this->isBadVersion($n)) {
+            if(!$this->isBadVersion($n - 1)) {
+                return $n;
+            }
+            else {
+                $position2check = ceil($n / 2);
+                $this->_right = $n;
+                //print __LINE__ . ': ' . $position2check . PHP_EOL;
+                return $this->firstBadVersion($position2check);
+            }
+        }
+        else {
+            if($this->isBadVersion($n + 1)) {
+                return $n + 1;
+            }
+            $position2check = ceil(($n + $this->_right) / 2);
+            //print __LINE__ . ': ' . $position2check . PHP_EOL;
+            return $this->firstBadVersion($position2check);
+        }
+    }
+}
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diff --git a/src/SearchInsertPosition/Solution.php b/src/SearchInsertPosition/Solution.php
new file mode 100644
index 0000000..1151673
--- /dev/null
+++ b/src/SearchInsertPosition/Solution.php
@@ -0,0 +1,39 @@
+<?php
+
+/**
+ * Project: leetcode
+ * Problem URL: https://leetcode.com/problems/search-insert-position/
+ * Difficulty: Easy
+ * Description: Given a sorted array of distinct integers and a target value, return the index if the target is found. If not, return the index where it would be if it were inserted in order.
+ * You must write an algorithm with O(log n) runtime complexity.
+ * Author: Igor Karpov <igorok.karpov@gmail.com>
+ * Date: 30.07.21
+ * Time: 11:14
+ * Class Solution
+ * @package Leetcode\MergeTwoSortedLists
+ */
+
+
+namespace Leetcode\SearchInsertPosition;
+
+class Solution
+{
+    /**
+     * @param Integer[] $nums
+     * @param Integer $target
+     * @return Integer
+     */
+    function searchInsert($nums, $target) {
+        if(sizeof($nums)) {
+            foreach ($nums as $key => $current) {
+                if($current >= $target) {
+                    return $key;
+                }
+            }
+            return ++$key;
+        }
+        else {
+            return 0;
+        }
+    }
+}
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