input: Write a function that calculates the permutation difference between two strings s and t, where each character occurs at most once and t is a rearrangement of s. The permutation difference is the total sum of the absolute differences between the indices of each character in s and its corresponding index in t. Return the permutation difference.
  
  Examples:
  >>> s = "abc", t = "bac"
  2
  >>> s = "abcde", t = "edbac"
  12
  
  Constraints:
  1 <= s.length <= 26
  Each character appears at most once in s.
  t is a rearrangement of s.
  s contains only lowercase English letters.
output: def permutation_difference(s, t):
      return sum(abs(i - t.index(c)) for i, c in enumerate(s))