diff --git a/librerie/exercise4/bst/bst.cpp b/librerie/exercise4/bst/bst.cpp
index db91a14..c84d4c4 100755
--- a/librerie/exercise4/bst/bst.cpp
+++ b/librerie/exercise4/bst/bst.cpp
@@ -324,7 +324,7 @@ typename BST<Data>::NodeLnk* const* BST<Data>::FindPointerToPredecessor(struct B
 
 
     Note: I return a ** instead of *& because we deferenciate a variable that might
-    contain nullptr (lastRight) that, without proper handling, would result to
+    contain nullptr (candidate) that, without proper handling, would result to
     an invalid read. I decided to keep it simpler to understand.
   */
 
diff --git a/librerie/exercise4/build.sh b/librerie/exercise4/build.sh
index 1f825de..cf5567b 100755
--- a/librerie/exercise4/build.sh
+++ b/librerie/exercise4/build.sh
@@ -1,7 +1,7 @@
 
 #! /bin/bash
 
-g++-10 -o main \
+g++ -O3 -o main \
   zlasdtest/exercise1/simpletest.cpp zlasdtest/exercise1/fulltest.cpp \
   zlasdtest/exercise2/simpletest.cpp zlasdtest/exercise2/fulltest.cpp \
   zlasdtest/exercise3/simpletest.cpp zlasdtest/exercise3/fulltest.cpp \
diff --git a/librerie/exercise4/zlasdtest/binarytree/binarytree.hpp b/librerie/exercise4/zlasdtest/binarytree/binarytree.hpp
old mode 100755
new mode 100644
diff --git a/librerie/exercise4/zlasdtest/bst/bst.hpp b/librerie/exercise4/zlasdtest/bst/bst.hpp
old mode 100755
new mode 100644
diff --git a/librerie/exercise4/zlasdtest/container/container.cpp b/librerie/exercise4/zlasdtest/container/container.cpp
old mode 100755
new mode 100644
diff --git a/librerie/exercise4/zlasdtest/container/container.hpp b/librerie/exercise4/zlasdtest/container/container.hpp
old mode 100755
new mode 100644
diff --git a/librerie/exercise4/zlasdtest/exercise1/fulltest.cpp b/librerie/exercise4/zlasdtest/exercise1/fulltest.cpp
old mode 100755
new mode 100644
diff --git a/librerie/exercise4/zlasdtest/exercise1/simpletest.cpp b/librerie/exercise4/zlasdtest/exercise1/simpletest.cpp
old mode 100755
new mode 100644
diff --git a/librerie/exercise4/zlasdtest/exercise1/test.hpp b/librerie/exercise4/zlasdtest/exercise1/test.hpp
old mode 100755
new mode 100644
diff --git a/librerie/exercise4/zlasdtest/exercise2/fulltest.cpp b/librerie/exercise4/zlasdtest/exercise2/fulltest.cpp
old mode 100755
new mode 100644
diff --git a/librerie/exercise4/zlasdtest/exercise2/simpletest.cpp b/librerie/exercise4/zlasdtest/exercise2/simpletest.cpp
old mode 100755
new mode 100644
diff --git a/librerie/exercise4/zlasdtest/exercise2/test.hpp b/librerie/exercise4/zlasdtest/exercise2/test.hpp
old mode 100755
new mode 100644
diff --git a/librerie/exercise4/zlasdtest/exercise3/fulltest.cpp b/librerie/exercise4/zlasdtest/exercise3/fulltest.cpp
old mode 100755
new mode 100644
diff --git a/librerie/exercise4/zlasdtest/exercise3/simpletest.cpp b/librerie/exercise4/zlasdtest/exercise3/simpletest.cpp
old mode 100755
new mode 100644
diff --git a/librerie/exercise4/zlasdtest/exercise3/test.hpp b/librerie/exercise4/zlasdtest/exercise3/test.hpp
old mode 100755
new mode 100644
diff --git a/librerie/exercise4/zlasdtest/exercise4/fulltest.cpp b/librerie/exercise4/zlasdtest/exercise4/fulltest.cpp
old mode 100755
new mode 100644
diff --git a/librerie/exercise4/zlasdtest/exercise4/test.hpp b/librerie/exercise4/zlasdtest/exercise4/test.hpp
old mode 100755
new mode 100644
diff --git a/librerie/exercise4/zlasdtest/iterator/iterator.hpp b/librerie/exercise4/zlasdtest/iterator/iterator.hpp
old mode 100755
new mode 100644
diff --git a/librerie/exercise4/zlasdtest/list/list.hpp b/librerie/exercise4/zlasdtest/list/list.hpp
old mode 100755
new mode 100644
diff --git a/librerie/exercise4/zlasdtest/queue/queue.hpp b/librerie/exercise4/zlasdtest/queue/queue.hpp
old mode 100755
new mode 100644
diff --git a/librerie/exercise4/zlasdtest/stack/stack.hpp b/librerie/exercise4/zlasdtest/stack/stack.hpp
old mode 100755
new mode 100644
diff --git a/librerie/exercise4/zlasdtest/test.cpp b/librerie/exercise4/zlasdtest/test.cpp
old mode 100755
new mode 100644
diff --git a/librerie/exercise4/zlasdtest/test.hpp b/librerie/exercise4/zlasdtest/test.hpp
old mode 100755
new mode 100644
diff --git a/librerie/exercise4/zlasdtest/vector/vector.hpp b/librerie/exercise4/zlasdtest/vector/vector.hpp
old mode 100755
new mode 100644
diff --git a/librerie/exercise4/zmytest/test.cpp b/librerie/exercise4/zmytest/test.cpp
index 87a6179..201fec9 100755
--- a/librerie/exercise4/zmytest/test.cpp
+++ b/librerie/exercise4/zmytest/test.cpp
@@ -611,7 +611,7 @@ bool NodeOperations(T& currentNode){
   do{
     cout<<" *** Element in the current node: "<<currentNode.Element()<<" ***"<<endl;
     cout<<" 1. Go left"<<endl;
-    cout<<" 2. Go Right"<<endl;
+    cout<<" 2. Go right"<<endl;
     cout<<" 3. Is this a leaf?"<<endl;
     cout<<" 4. Go up"<<endl;
     cout<<" 5. Go to menu"<<endl;
@@ -659,7 +659,7 @@ BST<int> GenerateIntegerBST(BST<int>& bst){
   default_random_engine gen(random_device{}());
   uniform_int_distribution<int> dist(0,1000);
 
-  cout<<"\n\nElements in the binary tree (in order of insertion):\n";
+  cout<<"\n\nElements in the binary search tree (in order of insertion):\n";
   for(ulong i=0 ; i<dim ; ++i){
     tmp[i] = dist(gen);
     cout<<tmp[i]<<" ";
@@ -677,7 +677,7 @@ BST<float> GenerateFloatBST(BST<float>& bst){
   default_random_engine gen(random_device{}());
   uniform_real_distribution<double> distr(0,5);
 
-  cout<<"\n\nElements in the binary tree (in breadth order):\n";
+  cout<<"\n\nElements in the binary search tree (in order of insertion):\n";
   for(unsigned long i = 0; i < dim; ++i){
     tmp[i] = (round(distr(gen)*10000))/100;
     cout<<tmp[i]<<" ";
@@ -695,7 +695,7 @@ BST<string> GenerateStringsBST(BST<string>& bst){
   default_random_engine gen(random_device{}());
   uniform_int_distribution<int> dist(1,5);
 
-  cout<<"\n\nElements in the tree (in breadth order):\n";
+  cout<<"\n\nElements in the binary search tree (in order of insertion):\n";
   for(ulong i = 0; i < dim; ++i){
     tmp[i] = generateRandomString(dist(gen));
     cout<<tmp[i]<<" ";