s = input()
s+=" "
n=len(s)
ans=0
c=0
m=0
a=s[0]
for i in range(n):
        if s[i]!=a:
                if c%3==0:
                        ans+=(c//3)*2;
                else:
                        ans+=1+(c//3)*2
                 if m==2 and c%3==2:
                         ans+=1
                        m=0
                elif c%3!=0:
                        m=c%3
                c=1
        else:
                c+=1
	a=s[i]
print(ans)