diff --git a/Assignment_3/lib/CMakeLists.txt b/Assignment_3/lib/CMakeLists.txt
index 12db947..7dd4299 100644
--- a/Assignment_3/lib/CMakeLists.txt
+++ b/Assignment_3/lib/CMakeLists.txt
@@ -1 +1 @@
-add_library(sets STATIC ADT_Stack.h ADT_Stack.cpp Node.h Node.cpp Stack.h Stack.cpp )
+add_library(sets STATIC ADT_Stack.h ADT_Stack.cpp Node.h Node.cpp Stack.h Stack.cpp SimpleLockingStack.h SimpleLockingStack.cpp)
diff --git a/Assignment_3/lib/SimpleLockingStack.cpp b/Assignment_3/lib/SimpleLockingStack.cpp
new file mode 100644
index 0000000..80c397a
--- /dev/null
+++ b/Assignment_3/lib/SimpleLockingStack.cpp
@@ -0,0 +1,26 @@
+#include "SimpleLockingStack.h"
+#include "ADT_Stack.h"
+
+SimpleLockingStack::SimpleLockingStack(ADTOperationQueue * queue) : Stack(queue) { }
+
+void SimpleLockingStack::push(int element) { 
+    mut.lock();
+    vec.push_back(element);
+    op_queue->enqueue(create_operation(methodname::push, element));
+    mut.unlock();
+}
+int SimpleLockingStack::pop() {
+    mut.lock();
+    int e = vec.back();
+    vec.pop_back();
+    op_queue->enqueue(create_operation(methodname::pop, e));
+    mut.unlock();
+    return e;
+}
+int SimpleLockingStack::size() { 
+    mut.lock();
+    int s = vec.size();
+    op_queue->enqueue(create_operation(methodname::size, s));
+    mut.unlock();
+    return s;    
+}
\ No newline at end of file
diff --git a/Assignment_3/lib/SimpleLockingStack.h b/Assignment_3/lib/SimpleLockingStack.h
new file mode 100644
index 0000000..b1768d7
--- /dev/null
+++ b/Assignment_3/lib/SimpleLockingStack.h
@@ -0,0 +1,16 @@
+
+#include <vector>
+#include <mutex>
+
+#include "Stack.h"
+
+class SimpleLockingStack:public Stack{
+    private:
+        std::vector<int> vec;
+        std::mutex mut;
+    public:
+        SimpleLockingStack(ADTOperationQueue * queue);
+        void push(int element);
+        int pop();
+        int size();
+};
\ No newline at end of file
diff --git a/Assignment_3/main.cpp b/Assignment_3/main.cpp
index b8f74db..40008c7 100644
--- a/Assignment_3/main.cpp
+++ b/Assignment_3/main.cpp
@@ -1,9 +1,11 @@
 #include <chrono>
 #include <iostream>
 #include <stdlib.h>  
+#include <thread>
 
 #include <lib/ADT_Stack.h>
 #include <lib/Stack.cpp>
+#include <lib/SimpleLockingStack.h>
 
 using namespace std::chrono;
 
@@ -18,6 +20,10 @@ using namespace std::chrono;
 #define OP_COUNT 100000
 #define THREADS 4
 
+int done_count = 0;
+std::mutex done_mutex;
+ADTOperationQueue * op_queue = new ADTOperationQueue();
+
 std::vector<operation> generate_operations_uniform(){
     operation default_operation = create_operation(methodname::push, 0);
     std::vector<operation> operations(OP_COUNT, default_operation);
@@ -44,10 +50,11 @@ std::vector<operation> generate_operations_uniform(){
     return operations;
 }
 
-void run_worker(std::vector<operation>* operations, Stack* stack) {    
+void run_worker(Stack* stack) {
+    std::vector<operation> operations = generate_operations_uniform();
     std::cout << "Worker: start" << std::endl;
     long op_counter = 0;
-    for (operation op : *operations) {
+    for (operation op : operations) {
         switch (op.method) {
             case methodname::pop:
                 stack->pop();
@@ -60,20 +67,21 @@ void run_worker(std::vector<operation>* operations, Stack* stack) {
                 break;
         }
     }
-
-     std::cout << "Worker: done" << std::endl;
+    done_mutex.lock();
+    done_count ++;
+    done_mutex.unlock();
+    std::cout << "Worker: done" << std::endl;
 }
 
-void run_checker(ADTOperationQueue queue, int* done_count) {
+void run_checker() {
     ADTStack * adt_stack = new ADTStack();
     while(true) {
-        int finished = *done_count;
-        size_t queue_size = queue.size();
+        size_t queue_size = op_queue->size();
         
-        if (finished >= THREADS && queue_size == 0) {
+        if (done_count >= THREADS && queue_size == 0) {
             break;
-        } else {
-            operation op = queue.dequeue();
+        } else if(queue_size != 0){
+            operation op = op_queue->dequeue();
             adt_stack->do_op(&op);
         }
     }
@@ -81,5 +89,20 @@ void run_checker(ADTOperationQueue queue, int* done_count) {
 }
 
 int main(){
+    Stack * s = new SimpleLockingStack(op_queue);
+
+    std::thread *worker= new std::thread[THREADS];
+
+    for (int i=0;i<THREADS;i++){
+        worker[i]=std::thread(run_worker, s);		
+    }
+
+    std::thread monitor = std::thread(run_checker);
+
+    for (int i=0;i<THREADS;i++){
+        worker[i].join();	
+    }
+
+    monitor.join();	
     return 0;
 }
\ No newline at end of file