import sys


def main():
    input = lambda: sys.stdin.readline()[:-1]
    N = int(input())
    S = "_" + input()

    ans = "BB" in S
    for i in range(1, N):
        if S[i : i + 2] == "BB" or S[i - 1 : i + 2] == "BAB":
            continue
        ans += 1

    print(ans)


if not __debug__:
    f = open(sys.argv[1], "r")
    sys.stdin = f

main()