N = int(input())
S = input()
ans = 0
# AA→BB
for i in range(N - 1):
    if S[i:i + 2] == "AA":
        ans += 1

# A→B
for i in range(N):
    if S[i] == "A":
        if (0 <= i - 1 and S[i - 1] == "B") or (i + 1 < N and S[i + 1] == "B"):
            ans += 1
# 不変
for i in range(N - 1):
    if S[i:i + 2] == "BB":
        ans += 1
        break
print(ans)