# -*- coding: utf-8 -*-

import bisect

import heapq

import math

import random

import sys

from collections import Counter, defaultdict, deque

from decimal import ROUND_CEILING, ROUND_HALF_UP, Decimal

from functools import lru_cache, reduce

from itertools import combinations, combinations_with_replacement, product, permutations

from operator import add, mul, sub



sys.setrecursionlimit(100000)





def read_int():

    return int(input())





def read_int_n():

    return list(map(int, input().split()))





def read_float():

    return float(input())





def read_float_n():

    return list(map(float, input().split()))





def read_str():

    return input().strip()





def read_str_n():

    return list(map(str, input().split()))





def error_print(*args):

    print(*args, file=sys.stderr)





def mt(f):

    import time



    def wrap(*args, **kwargs):

        s = time.time()

        ret = f(*args, **kwargs)

        e = time.time()



        error_print(e - s, 'sec')

        return ret



    return wrap





class Mod:

    def __init__(self, m):

        self.m = m

    

    def add(self, a, b):

        return (a + b ) % self.m



    def sub(self, a, b):

        return (a - b) % self.m

    

    def mul(self, a, b):

        return ((a % self.m) * (b % self.m)) % self.m



    def div(self, a, b):

        return self.mul(a, self.pow(b, self.m-2))



    def pow(self, x, y):

        if y == 0: 

            return 1

        elif y == 1: 

            return x % self.m

        elif y % 2 == 0: 

            return self.pow(x, y//2)**2 % self.m

        else: 

            return self.pow(x, y//2)**2 * x % self.m







@mt

def slv(N, S):



    ans = 0

    CC = Counter()

    for c in S:

        CC[c] += 1

    

    m = Mod(10**9+7)



    cs = tuple(CC.values())

    @lru_cache(maxsize=None)

    def f(v):

        if not v:

            return 1

        

        c = v[0]

        v = v[1:]

        return m.add(m.mul(c, f(v)), f(v))

    return f(cs) - 1





def main():

    N = read_int()

    S = read_str()

    print(slv(N, S))





if __name__ == '__main__':

    main()

# -*- coding: utf-8 -*-

import bisect

import heapq

import math

import random

import sys

from collections import Counter, defaultdict, deque

from decimal import ROUND_CEILING, ROUND_HALF_UP, Decimal

from functools import lru_cache, reduce

from itertools import combinations, combinations_with_replacement, product, permutations

from operator import add, mul, sub



sys.setrecursionlimit(100000)





def read_int():

    return int(input())





def read_int_n():

    return list(map(int, input().split()))





def read_float():

    return float(input())





def read_float_n():

    return list(map(float, input().split()))





def read_str():

    return input().strip()





def read_str_n():

    return list(map(str, input().split()))





def error_print(*args):

    print(*args, file=sys.stderr)





def mt(f):

    import time



    def wrap(*args, **kwargs):

        s = time.time()

        ret = f(*args, **kwargs)

        e = time.time()



        error_print(e - s, 'sec')

        return ret



    return wrap





class Mod:

    def __init__(self, m):

        self.m = m

    

    def add(self, a, b):

        return (a + b ) % self.m



    def sub(self, a, b):

        return (a - b) % self.m

    

    def mul(self, a, b):

        return ((a % self.m) * (b % self.m)) % self.m



    def div(self, a, b):

        return self.mul(a, self.pow(b, self.m-2))



    def pow(self, x, y):

        if y == 0: 

            return 1

        elif y == 1: 

            return x % self.m

        elif y % 2 == 0: 

            return self.pow(x, y//2)**2 % self.m

        else: 

            return self.pow(x, y//2)**2 * x % self.m







@mt

def slv(N, S):

    CC = Counter()

    for c in S:

        CC[c] += 1



    for c in CC:

        CC[c] += 1

    

    m = Mod(10**9+7)

    return reduce(m.mul, CC.values()) - 1





def main():

    N = read_int()

    S = read_str()

    print(slv(N, S))





if __name__ == '__main__':

    main()

# -*- coding: utf-8 -*-
import bisect
import heapq
import math
import random
import sys
from collections import Counter, defaultdict, deque
from decimal import ROUND_CEILING, ROUND_HALF_UP, Decimal
from functools import lru_cache, reduce
from itertools import combinations, combinations_with_replacement, product, permutations
from operator import add, mul, sub

sys.setrecursionlimit(100000)


def read_int():
    return int(input())


def read_int_n():
    return list(map(int, input().split()))


def read_float():
    return float(input())


def read_float_n():
    return list(map(float, input().split()))


def read_str():
    return input().strip()


def read_str_n():
    return list(map(str, input().split()))


def error_print(*args):
    print(*args, file=sys.stderr)


def mt(f):
    import time

    def wrap(*args, **kwargs):
        s = time.time()
        ret = f(*args, **kwargs)
        e = time.time()
        error_print(e - s, "sec")
        return ret

    return wrap


class Mod:
    def __init__(self, m):
        self.m = m

    def add(self, a, b):
        return (a + b) % self.m

    def sub(self, a, b):
        return (a - b) % self.m

    def mul(self, a, b):
        return ((a % self.m) * (b % self.m)) % self.m

    def div(self, a, b):
        return self.mul(a, self.pow(b, self.m - 2))

    def pow(self, x, y):
        if y == 0:
            return 1
        elif y == 1:
            return x % self.m
        elif y % 2 == 0:
            return self.pow(x, y // 2) ** 2 % self.m
        else:
            return self.pow(x, y // 2) ** 2 * x % self.m


@mt
def slv(N, S):
    ans = 0
    CC = Counter()
    for c in S:
        CC[c] += 1
    m = Mod(10**9 + 7)
    cs = tuple(CC.values())

    @lru_cache(maxsize=None)
    def f(v):
        if not v:
            return 1
        c = v[0]
        v = v[1:]
        return m.add(m.mul(c, f(v)), f(v))

    return f(cs) - 1


def main():
    N = read_int()
    S = read_str()
    print(slv(N, S))


if __name__ == "__main__":
    main()

# -*- coding: utf-8 -*-
import bisect
import heapq
import math
import random
import sys
from collections import Counter, defaultdict, deque
from decimal import ROUND_CEILING, ROUND_HALF_UP, Decimal
from functools import lru_cache, reduce
from itertools import combinations, combinations_with_replacement, product, permutations
from operator import add, mul, sub

sys.setrecursionlimit(100000)


def read_int():
    return int(input())


def read_int_n():
    return list(map(int, input().split()))


def read_float():
    return float(input())


def read_float_n():
    return list(map(float, input().split()))


def read_str():
    return input().strip()


def read_str_n():
    return list(map(str, input().split()))


def error_print(*args):
    print(*args, file=sys.stderr)


def mt(f):
    import time

    def wrap(*args, **kwargs):
        s = time.time()
        ret = f(*args, **kwargs)
        e = time.time()
        error_print(e - s, "sec")
        return ret

    return wrap


class Mod:
    def __init__(self, m):
        self.m = m

    def add(self, a, b):
        return (a + b) % self.m

    def sub(self, a, b):
        return (a - b) % self.m

    def mul(self, a, b):
        return ((a % self.m) * (b % self.m)) % self.m

    def div(self, a, b):
        return self.mul(a, self.pow(b, self.m - 2))

    def pow(self, x, y):
        if y == 0:
            return 1
        elif y == 1:
            return x % self.m
        elif y % 2 == 0:
            return self.pow(x, y // 2) ** 2 % self.m
        else:
            return self.pow(x, y // 2) ** 2 * x % self.m


@mt
def slv(N, S):
    CC = Counter()
    for c in S:
        CC[c] += 1
    for c in CC:
        CC[c] += 1
    m = Mod(10**9 + 7)
    return reduce(m.mul, CC.values()) - 1


def main():
    N = read_int()
    S = read_str()
    print(slv(N, S))


if __name__ == "__main__":
    main()

-    ans = 0 +    for c in CC: +        CC[c] += 1 -    cs = tuple(CC.values()) - -    @lru_cache(maxsize=None) -    def f(v): -        if not v: -            return 1 -        c = v[0] -        v = v[1:] -        return m.add(m.mul(c, f(v)), f(v)) - -    return f(cs) - 1 +    return reduce(m.mul, CC.values()) - 1