n = int(input())

if n < 5:
	print(0)
	exit()

S = input()

ans = 0
for i0 in range(n):
	for i1 in range(i0 + 1, n):
		for i2 in range(i1 + 1, n):
			for i3 in range(i2 + 1, n):
				for i4 in range(i3 + 1, n):
	
					a = S[i0] + S[i1] + S[i2] + S[i3] + S[i4];
	
					if a[0] == a[2] and len(set(a)) == 4:
						ans += 1

print(ans)