N = int(input())
S = input().strip()
A = set()
S1 = list(S)
for i in range(N-1):
    S1[i],S1[i+1] = "B","B"
    A.add("".join(S1))
    S1[i],S1[i+1] = S[i],S[i+1]
print(len(A))