import itertools

def is_cpctf_like(s):
    # Check length first (must be 5)
    if len(s) != 5:
        return False
    # Check S1 == S3
    if s[0] != s[2]:
        return False
    # Check uniqueness of other positions (1, 3, 4)
    # Only s[0] and s[2] can be the same, rest must be unique
    positions = [s[0], s[1], s[2], s[3], s[4]]
    return len(positions) == len(set(positions)) + 1  # because s[0] == s[2]

def count_cpctf_like_subsequences(n, s):
    count = 0
    # Generate all index combinations of 5 characters (non-contiguous allowed)
    for indices in itertools.combinations(range(n), 5):
        sub = ''.join(s[i] for i in indices)
        if is_cpctf_like(sub):
            count += 1
    return count

# Input
n = int(input())
s = input().strip()

# Output
print(count_cpctf_like_subsequences(n, s))