N = int(input())
S = input()

ans = 0
for i in range(len(S) - 1):
    if S[i] == "A":
        if S[i+1] == "A":
            ans += 1
        else:
            if i > 0 and S[i-1] == "A":
                ans += 1
    else:
        if S[i+1] == "A":
            ans += 1
print(ans)