diff --git a/src/index.js b/src/index.js
index 243d154..8eeffdd 100644
--- a/src/index.js
+++ b/src/index.js
@@ -5,7 +5,16 @@
  */
 
 const hammingDistance = (a, b) => {
-    
+  let hamming = 0;  
+  if(a.length != b.length){
+    throw Error;
+  }
+  for(let letter = 0; letter <a.length; letter++){
+    if(a[letter] != b[letter]){
+      hamming++;
+    }
+  }
+  return hamming
   }
   
   module.exports = hammingDistance;
\ No newline at end of file