add logic for joined or separated audio and video

skilldown.py

@@ -5,6 +5,10 @@ import wget as wget
 from urllib.request import urlopen
 from urllib.error import HTTPError
 
+sep = input("Are audio and video in the Same or Different files? [S|D]")
+sep = sep.lower()
+if not(sep=='s' or sep=='d'):
+	raise ValueError("The answer should be S or D")
 #video
 i=0
 while True: