diff --git a/Problem1.java b/Problem1.java
index 8b137891..2ae31cbb 100644
--- a/Problem1.java
+++ b/Problem1.java
@@ -1 +1,27 @@
+//Time Complexity: O(log n)
+//Space Complexity: O(1)
+// Did this code successfully run on Leetcode :yes
+// Any problem you faced while coding this :no
 
+// Before the missing element: arr[i] == i+1
+// After the missing index: arr[i] == i+2
+// So the missing number is i+1 at the first index where this occurs.
+
+
+class Problem1{
+    int missingNumber(int arr[]){
+        int low,high,mid;
+        low=0;
+        high = arr.length-1;
+        while(low<=high){
+            mid=low+(high-low)/2;
+            if(arr[mid]==mid+1){
+                low=mid+1;//missing element is in right side
+            }
+            else{
+                high=mid-1;//missing element is in left side
+            }
+        }
+        return low+1;
+    }
+}