diff --git a/src/index.js b/src/index.js
index 243d154..55a20f5 100644
--- a/src/index.js
+++ b/src/index.js
@@ -5,7 +5,23 @@
  */
 
 const hammingDistance = (a, b) => {
-    
+ 
+  let hammingDistance = 0
+  
+  if (a.length == b.length) {
+
+    for (i = 0; i < a.length; i++) {
+
+      if(a.charAt(i) !== b.charAt(i)) {
+        hammingDistance++
+      }
+    }
+  } else {
+    throw new Error('Sorry, I can not to compare it')
+  }
+
+  return hammingDistance;
+}
   }
   
-  module.exports = hammingDistance;
\ No newline at end of file
+  module.exports = hammingDistance;