N = int(input())
S = input()
ans = N - 1
cntBB = 0
cntBAB = 0
for i in range(N - 1):
    if S[i:i + 2] == "BB":
        cntBB += 1
    if i < N - 2 and S[i:i + 3] == "BAB":
        cntBAB += 1
ans -= max(0,cntBB-1)
ans -= cntBAB
print(ans)