diff --git a/Problem1.java b/Problem1.java
index 8b137891..7a6eb579 100644
--- a/Problem1.java
+++ b/Problem1.java
@@ -1 +1,37 @@
+// Time Complexity : O(log N)
+// Space Complexity : O(1)
+// Did this code successfully run on Leetcode Playground : Yes
+// Any problem you faced while coding this : No
 
+public class GfG {
+    static int missingNumber(int[] arr) {
+        int n = arr.length;
+
+        // Edge cases
+        if (arr[0] != 1) {
+            return 1;
+        }
+        if (arr[n - 1] != (n + 1)) {
+            return n + 1;
+        }
+
+        // binary search
+        int low = 0, high = n - 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;
+    }
+
+    public static void main(String[] args) {
+        int[] arr = {1, 2, 3, 4, 6, 7, 8};
+        System.out.println(missingNumber(arr));
+    }
+}
\ No newline at end of file