from itertools import combinations

def is_ok(s, input):

    a, b, c, d, e = input
    chars = [s[a], s[b], s[c], s[d], s[e]]
    
    # 1文字目と3文字目が同じ
    if chars[0] != chars[2]:
        return False

    # 1文字目と3文字目以外が全部異なる
    other_chars = [chars[1], chars[3], chars[4]]
    if len(set(other_chars)) != 3:
        return False
    
    # 1文字目と3文字目以外が、1文字目と3文字目とは違う
    if chars[0] in other_chars:
        return False
    return True

def count_cpstf(S):
    N = len(S)
    count = 0
    for input in combinations(range(N), 5):
        if is_ok(S, input):
            count += 1
    return count

N = int(input())
S = input().strip()

print(count_cpstf(S))