import sys
#input = sys.stdin.readline
#input = sys.stdin.buffer.readline #文字列はダメ
#sys.setrecursionlimit(1000000)
#import bisect
#import itertools
#import random
#from heapq import heapify, heappop, heappush
#from collections import defaultdict 
#from collections import deque
#import copy
#import math
#from functools import lru_cache
#@lru_cache(maxsize=None)
#MOD = pow(10,9) + 7
#MOD = 998244353
#dx = [1,0,-1,0]
#dy = [0,1,0,-1]
#dx8 = [1,1,0,-1,-1,-1,0,1]
#dy8 = [0,1,1,1,0,-1,-1,-1]

def main():
    N = int(input())
    S = str(input())

    ans = N-1
    same = 0
    st = set([])
    for i in range(N-1):
        two = S[i:i+2]
        if two == 'BB':
            same += 1
        # temp = S[:i] + "BB" + S[i+2:]
        # print(temp)
        # st.add(temp)
        if i < N-2:
            three = S[i:i+3]
            if three == 'BAB' or three == 'BBB':
                ans -= 1
                # print("X")
    ans -= max(0,same-1)
    print(ans)
    # print(len(st))

if __name__ == '__main__':
    main()