diff --git a/Problem1.py b/Problem1.py
new file mode 100644
index 00000000..3ce8eaea
--- /dev/null
+++ b/Problem1.py
@@ -0,0 +1,20 @@
+class Solution:
+    def missingNumber(self, arr):
+        # code here
+        if len(arr) == 1:
+            return len(arr)
+            
+        low, high = 0 , len(arr)-1
+        while low < high:
+            mid = (low+high)//2
+            #verify left half
+            if arr[mid] == mid+1: #O(c)
+                low = mid + 1
+            else: #verify right half
+                high = mid - 1
+        
+        if (low == 0 and arr[low] == 1) or arr[low] == low+1: 
+            return arr[low] + 1
+        
+        return arr[low] - 1
+
diff --git a/README.md b/README.md
index d3394c1a..306b32ab 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,21 @@
 # Competitive-Coding-1
 
 Please submit the interview problems posted in slack channel here. The problems and statements are intentionally not shown here so that students are not able to see them in advance 
+
+Missing Number in Sorted Array of Natural Numbers
+Difficulty: EasyAccuracy: 55.26%Submissions: 2K+Points: 2
+Given a sorted array arr[] of n-1 integers, these integers are in the range of 1 to n. There are no duplicates in the array. One of the integers is missing in the array. Find the missing integer.
+
+Examples:
+
+Input: arr[] = [1, 2, 3, 4, 6, 7, 8]
+Output: 5
+Explanation: The missing integer in the array is 5.
+Input: arr[] = [1, 2, 3, 4, 5, 6, 8, 9]
+Output: 7
+Explanation: The missing integer in the array is 7.
+Constraints:
+1 ≤ arr.size() ≤ 105
+1 ≤ arr[i] ≤ arr.size()+1
+
+