def is_cpctf(s):
    if s[0] != s[2]:
        return False
    
    for i in range(5):
        for j in range(i+1, 5):
            if (i, j) == (0, 2):
                continue
            
            if s[i] == s[j]:
                return False
    
    return True

N = int(input())
S = input()

count = 0
    
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):
                    substr = S[i1] + S[i2] + S[i3] + S[i4] + S[i5]
                    if is_cpctf(substr):
                        count += 1

print(count)