eg.
Reference :Edit Distance wikipedia
eg.
  1. kitten → sitten (substitution of "s" for "k")
  2. sitten → sittin (substitution of "i" for "e")
  3. sittin → sitting (insertion of "g" at the end).
Cost=2+2+1=5
Instantiation 2.
Cost of deletion ,insertion and substitution  is equal to 1 . This Distance is also known as    Wagner-Fischer distance
Reference:Wagner Fischer wikipedia