n = int(input())
s = input().strip()
count = 0

# We need to select 5 distinct indices i1 < i2 < i3 < i4 < i5 in the string s
# such that s[i1] == s[i3], and all other characters (s[i2], s[i4], s[i5]) are distinct and != s[i1]

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):
                    # Check if s[i1] == s[i3]
                    if s[i1] == s[i3]:
                        # Check other conditions
                        a, b, c, d, e = s[i1], s[i2], s[i3], s[i4], s[i5]
                        # a == c is already true
                        # b, d, e must be distinct and != a
                        if b != a and d != a and e != a:
                            if b != d and b != e and d != e:
                                count += 1

print(count)