N = int(input())
S = list(input())
ans_set = set()

for i in range(N-1):
    a,b = S[i],S[i+1]
    S[i],S[i+1] = "B","B"
    ans_set.add(tuple(S))
    S[i],S[i+1] = a,b

print(len(ans_set))