diff --git a/Problem1.java b/Problem1.java
index 8b137891..2ce33a2c 100644
--- a/Problem1.java
+++ b/Problem1.java
@@ -1 +1,44 @@
+class GfG {
 
+    static int missingNumber(int[] arr) {
+       int h = arr.length-1;
+      int l = 0;
+      int leftmissing = leftBinraySearch(arr, 0, l);
+      if(leftmissing != -1) return leftmissing;
+      int rightMissing = rightBinarySearch(arr, 0, 1);
+      return rightMissing;
+    }
+  	private int leftBinraySearch(int[] arr, int l, int h) {
+   		while(l <= h) {
+         int mid = l + (hi - l) /2;
+          if(arr[mid-1] +1 != arr[mid]) {
+           return arr[mid] -1;
+          } else if(arr[mid+1] -1 != arr[mid]) {
+            return arr[mid]+1;
+          } else {
+           h = mid -1; // binary left search
+          }
+        }
+      return -1;
+    }
+
+  private int rightBinarySearch(int[] arr, int l, int h) {
+    while(l <= h) {
+         int mid = l + (hi - l) /2;
+          if(arr[mid-1] +1 != arr[mid]) {
+           return arr[mid] -1;
+          } else if(arr[mid+1] -1 != arr[mid]) {
+            return arr[mid]+1;
+          } else {
+           l = mid +1; // binary right search
+          }
+        }
+      return -1;
+  }
+  	
+
+    public static void main(String[] args) {
+        int[] arr = {1, 2, 3, 4, 6, 7, 8};
+        System.out.println(missingNumber(arr));
+    }
+}