def solve(n, s):
    count = 0
    
    # 5つのインデックスを選ぶ全ての組み合わせを考える
    for i1 in range(n):
        for i2 in range(i1+1, n):
            for i3 in range(i2+1, n):
                for i4 in range(i3+1, n):
                    for i5 in range(i4+1, n):
                        # 選んだインデックスの文字を取得
                        chars = [s[i1], s[i2], s[i3], s[i4], s[i5]]
                        
                        # CPCTF的かチェック
                        # 1文字目と3文字目が同じ
                        if chars[0] == chars[2]:
                            # 他の位置の文字がすべて異なる
                            if (chars[0] != chars[1] and chars[0] != chars[3] and chars[0] != chars[4] and
                                chars[1] != chars[2] and chars[1] != chars[3] and chars[1] != chars[4] and
                                chars[2] != chars[3] and chars[2] != chars[4] and
                                chars[3] != chars[4]):
                                count += 1
    
    return count

# 入力を読み込む
n = int(input())
s = input().strip()

# 解を求める
result = solve(n, s)
print(result)