Problem:
Score : 200 points

Problem 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.

Constraints

1 \leq N \leq 100000

S consists of lowercase English letters.

|S|=N

Input

Input is given from Standard Input in the following format:

N
S

Output

Print the number of the subsequences such that all characters are different, modulo 10^9+7.

Sample Input 1

4
abcd

Sample Output 1

15

Since all characters in S itself are different, all its subsequences satisfy the condition.

Sample Input 2

3
baa

Sample Output 2

5

The answer is five: b, two occurrences of a, two occurrences of ba. Note that we do not count baa, since it contains two as.

Sample Input 3

5
abcab

Sample Output 3

17

Solution in C (Clang 3.8.0) (judge verdict: Wrong Answer)

int main(){
  
  int n;
    long product=1;
  int count[26]={0};
 
  
  scanf("%d",&n);
  
  char s[n];
 
  scanf("%s",s);
   
  
 
  for(int i=0;i<n;i++)
      count[s[i]-'a']++;
  
  
  for(int k=0;k<26;k++)
  product=product*(count[k]+1); 
    product=(product-1)%(1000000000+7);
  
  printf("%ld",product);
  
 return 0; 
  
}