def solve(n, s):
    count = 0
    
    # Try all possible combinations of 5 positions
    for i in range(n):
        for j in range(i+1, n):
            for k in range(j+1, n):
                for l in range(k+1, n):
                    for m in range(l+1, n):
                        # Check if characters at positions i and k are equal (1st and 3rd positions)
                        if s[i] == s[k]:
                            # Check if all other characters are different
                            if s[j] != s[i] and s[l] != s[i] and s[m] != s[i] and s[j] != s[l] and s[j] != s[m] and s[l] != s[m]:
                                count += 1
    
    return count

# Read input
n = int(input())
s = input()
print(solve(n, s))