diff --git a/Problem1.java b/Problem1.java
index 8b137891..3da29cd8 100644
--- a/Problem1.java
+++ b/Problem1.java
@@ -1 +1,23 @@
+// Find the missing number in a sorted array
+// Time complexity: O(log n)
+// Space complexity: O(1)
 
+class Solution {
+    int missingNumber(int arr[]) {
+        // code here
+        int low = 0;
+        int high = arr.length - 1;
+
+        while(low <= high){
+            int mid = low + (high - low) / 2;
+
+            if(arr[mid] != mid +1){
+                high = mid - 1;
+            }
+            else{
+                low = mid + 1;
+            }
+        }
+        return low + 1;
+    }
+}