import itertools

n = int(input())

li = [i for i in range(n)]
s = input()

comb = itertools.combinations(li, 5)

count = 0
for item in comb:
    tmp = s[item[0]] + s[item[1]] + s[item[2]] + s[item[3]] + s[item[4]]

    if (tmp[0] == tmp[2]) and (tmp[0] != tmp[1]) and (tmp[0] != tmp[3]) and (tmp[0] != tmp[4]) and (tmp[1] != tmp[3]) and (tmp[1] != tmp[4]) and (tmp[3] != tmp[4]):
        count += 1

print(count)