diff --git a/book/book_second_edition.pdf b/book/book_second_edition.pdf
index df51f16..34f3820 100644
Binary files a/book/book_second_edition.pdf and b/book/book_second_edition.pdf differ
diff --git a/src/builtin_structures/primes_generating.py b/src/builtin_structures/primes_generating.py
deleted file mode 100755
index 7f6f828..0000000
--- a/src/builtin_structures/primes_generating.py
+++ /dev/null
@@ -1,36 +0,0 @@
-#!/usr/bin/env python
-
-__author__ = "bt3"
-
-
-import math
-import random
-import sys
-from finding_prime import finding_prime_sqrt
-
-
-def generate_prime(number=3):
-    ''' return a n-bit prime '''
-    while 1:
-        p = random.randint(pow(2, number-2), pow(2, number-1)-1)
-        p = 2 * p + 1
-        if finding_prime_sqrt(p):
-            return p
-
-
-if __name__ == '__main__':
-    if len(sys.argv) < 2:
-        print ("Usage: generate_prime.py number")
-        sys.exit()
-    else:
-        number = int(sys.argv[1])
-        print(generate_prime(number))
-
-
-
-
-
-
-
-
-
diff --git a/src/trees/check_largest_item.py b/src/trees/check_largest_item.py
new file mode 100755
index 0000000..3428d60
--- /dev/null
+++ b/src/trees/check_largest_item.py
@@ -0,0 +1,23 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+
+from binary_search_tree import BST, Node
+
+def largest(node):
+
+    if node.right:
+        return largest(node.right)
+    return node.item
+
+
+if __name__ == '__main__':
+
+
+    bst = BST()
+    l = [10, 5, 6, 3, 8, 2, 1, 11, 9, 4]
+    for i in l:
+        bst.add(i)
+
+    print(largest(bst.root))