import math
n = int(input())
c = input()
l = []
r = []
for i in range(n):
	if r.count(c[i]) == 0:
		l.append(l.count(c[i]))
		r.apprnd(c[i])
if len(l) < 5 or math.prod(l) <= 1:
	print(0)
else:
	a = len(l) - l.count(1)
	b = len(l)
	ans = a * b * (b-1) /2
	print(int(ans))