Update README.md

Author: coder9051

README.md

@@ -83,8 +83,31 @@ print("The Encrypted message is: ", encrpyted_message)
 This code can only be used when we know key else we have try brute force method by trying for every key value. In this method we undo the previous code to get original message.
 
 ```python
+#Create a function for Decryption algorithm
+def decrpyt_message(text, key):
 
-```
+    decrypted_msg = "" # initially empty string is created
+
+    for char in text:    
+
+        if char.isupper(): # check character is uppercase
+            decrypted_msg += chr((((ord(char) - key) - 65) % 26) + 65)
+
+        elif char.islower(): # checks character is  lowercase
+            decrypted_msg += chr((((ord(char) -key) - 97) % 26) + 97)
+
+        else:
+            decrypted_msg += char # Number, spaces and special charcters are added as it is.
+
+    return decrypted_msg
 
+text = input("Please Enter your message: ") 
+key = int(input("Enter key value: "))
 
+print("Your message: ", text)
+
+decrpyted_message = decrpyt_message(text, key)
+print("The Decrypted message is: ", decrpyted_message)
+```
 
+## Conclusion