n=int(input())
s=input()
c=0
c+="BB" in s
for i in range(n-1):
	c+=s[i:i+2]=="AA"
for i in range(n-1):
	c+=s[i:i+2]=="AB"
for i in range(n-1):
	c+=s[i:i+2]=="BA"
for i in range(n-2):
	c-=s[i:i+3]=="BAB"
print(c)