from itertools import combinations
from collections import Counter

def is_cpctf(s):
    # s: 長さ5の文字列リスト ['A','B','A','C','D']
    if s[0] != s[2]:
        return False
    counter = Counter(s)
    return counter[s[0]] == 2 and all(count == 1 for ch, count in counter.items() if ch != s[0])

def count_cpctf_subsequences(N, S):
    count = 0
    indices = list(range(N))
    for comb in combinations(indices, 5):
        chars = [S[i] for i in comb]
        if is_cpctf(chars):
            count += 1
    return count

# 入力例
N = int(input())
S = input().strip()
print(count_cpctf_subsequences(N, S))