n = int(input())
S = input()
se = set()
for i in range(1, n):
    lst = []
    if S[i - 1] == "A":
        lst.append(i - 1)
    if S[i] == "A":
        lst.append(i)
    tot = 0
    for l in lst:
        tot *= n + 1
        tot += l + 1
    se.add(tot)
print(len(se))