output_description: Print the number of the subsequences such that all characters are different,
  modulo 10^9+7.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N
      S
attempt: N = int(input())
  S = input()
    
  co = 0
  index =0
  n =[]
  str = ""
  
  for i in range(N):
    index=str.find(S[i])
    if index == -1 :
      str += S[i]
      n.append(2)
    else :
      n[i]++
  
  co = 1
  for i in range(len(n)):
    co = co * n[i]
  co -= 1
  
  print(co % 1000000007)
problem_description: Statement
  
  You are given a string S of length N. Among its subsequences, count the ones
  such that all characters are different, modulo 10^9+7. Two subsequences are
  considered different if their characters come from different positions in the
  string, even if they are the same as strings.
  
  Here, a subsequence of a string is a concatenation of **one or more**
  characters from the string without changing the order.
samples: [{"input": "4\n    abcd", "output": "15\n    \n\nSince all characters in S itself are different, all its subsequences satisfy\nthe condition.\n\n* * *"}, {"input": "3\n    baa", "output": "5\n    \n\nThe answer is five: `b`, two occurrences of `a`, two occurrences of `ba`. Note\nthat we do not count `baa`, since it contains two `a`s.\n\n* * *"}, {"input": "5\n    abcab", "output": "17"}]