diff --git a/os/code/os/src/main/java/com/scaler/addersubtractor/Adder.java b/os/code/os/src/main/java/com/scaler/addersubtractor/Adder.java
new file mode 100644
index 0000000..d42c8f2
--- /dev/null
+++ b/os/code/os/src/main/java/com/scaler/addersubtractor/Adder.java
@@ -0,0 +1,22 @@
+package com.scaler.addersubtractor;
+
+import lombok.AllArgsConstructor;
+
+@AllArgsConstructor
+public class Adder implements Runnable {
+    private Count count;
+
+    @Override
+    public void run() {
+
+        for (int i = 1; i <= 100; ++i) {
+            count.getValue().getAndAdd(i);
+            try {
+                Thread.sleep(10);
+            } catch (Exception e) {
+                System.out.println("Something wrong happened");
+            }
+        }
+
+    }
+}
diff --git a/os/code/os/src/main/java/com/scaler/addersubtractor/Count.java b/os/code/os/src/main/java/com/scaler/addersubtractor/Count.java
new file mode 100644
index 0000000..348de30
--- /dev/null
+++ b/os/code/os/src/main/java/com/scaler/addersubtractor/Count.java
@@ -0,0 +1,15 @@
+package com.scaler.addersubtractor;
+
+import java.util.concurrent.atomic.AtomicInteger;
+
+public class Count {
+    private AtomicInteger value = new AtomicInteger(0);
+
+    public AtomicInteger getValue() {
+        return value;
+    }
+
+    public void setValue(AtomicInteger value) {
+        this.value = value;
+    }
+}
diff --git a/os/code/os/src/main/java/com/scaler/addersubtractor/Runner.java b/os/code/os/src/main/java/com/scaler/addersubtractor/Runner.java
new file mode 100644
index 0000000..795718c
--- /dev/null
+++ b/os/code/os/src/main/java/com/scaler/addersubtractor/Runner.java
@@ -0,0 +1,27 @@
+package com.scaler.addersubtractor;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+
+public class Runner {
+    public static void main(String[] args) {
+        Count count = new Count();
+
+        Adder adder = new Adder(count);
+        Subtractor subtractor = new Subtractor(count);
+
+        ExecutorService executor = Executors.newCachedThreadPool();
+        executor.execute(adder);
+        executor.execute(subtractor);
+
+        executor.shutdown();
+        try {
+            executor.awaitTermination(100, TimeUnit.SECONDS);
+        } catch (Exception e) {
+            System.out.println("Something wrong happened");
+        }
+
+        System.out.println(count.getValue());
+    }
+}
diff --git a/os/code/os/src/main/java/com/scaler/addersubtractor/Subtractor.java b/os/code/os/src/main/java/com/scaler/addersubtractor/Subtractor.java
new file mode 100644
index 0000000..ae80473
--- /dev/null
+++ b/os/code/os/src/main/java/com/scaler/addersubtractor/Subtractor.java
@@ -0,0 +1,28 @@
+package com.scaler.addersubtractor;
+
+import java.util.concurrent.locks.Lock;
+
+import lombok.AllArgsConstructor;
+
+@AllArgsConstructor
+public class Subtractor implements Runnable {
+    private Count count;
+
+    @Override
+    public void run() {
+
+        for (int i = 1; i <= 100; ++i) {
+            count.getValue().getAndAdd(-i);
+            try {
+                Thread.sleep(10);
+            } catch (Exception e) {
+                System.out.println("Something wrong happened");
+            }
+
+            for (int j = 0; j < 10000; ++j) {
+                // do something
+            }
+        }
+
+    }
+}
\ No newline at end of file