from itertools import combinations

n = input()
s = input()
c = 0
for t in combinations(s, 5):
    ok = False
    if t[0] == t[2]:
        ok = True
    for i in range(5):
        for j in range(i + 1, 5):
            if not (i == 0 and j == 2):
                if t[i] == t[j]:
                    ok = False
    c += int(ok)
print(c)