from collections import defaultdict
import sys
readline=sys.stdin.readline
write=sys.stdout.write

N=int(readline())
S=readline().rstrip()
ans=0
if "BB" in S:
    ans+=1
for n in range(N-1):
    if S[n:n+2]=="AA":
        ans+=1
for n in range(N):
    if S[n]=="A":
        if n and S[n-1]=="B" or n!=N-1 and S[n+1]=="B":
            ans+=1
print(ans)