import sys

sys.setrecursionlimit(10**6)
int1 = lambda x: int(x)-1
p2D = lambda x: print(*x, sep="\n")
def II(): return int(sys.stdin.buffer.readline())
def FI(): return float(sys.stdin.buffer.readline())
def MI(): return map(int, sys.stdin.buffer.readline().split())
def MF(): return map(float, sys.stdin.buffer.readline().split())
def MI1(): return map(int1, sys.stdin.buffer.readline().split())
def LI(): return list(map(int, sys.stdin.buffer.readline().split()))
def LI1(): return list(map(int1, sys.stdin.buffer.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def BI(): return sys.stdin.buffer.readline().rstrip()
def SI(): return sys.stdin.buffer.readline().rstrip().decode()
dij = [(0, 1), (-1, 0), (0, -1), (1, 0)]
inf = 10**16
# md = 998244353
md = 10**9+7

def RLE(s):
    cc=[]
    ww=[]
    pc=s[0]
    w=0
    for c in s:
        if c==pc:w+=1
        else:
            cc.append(pc)
            ww.append(w)
            w=1
            pc=c
    cc.append(pc)
    ww.append(w)
    return cc,ww

s="000"+SI()
cc,ww=RLE(s)

ans=0
one=False
for w0,w1 in zip(ww[::2],ww[1::2]):
    if w0>2:
        if w1==1:
            ans+=1
            one=True
        else:
            ans+=2
            one=False
    elif not one and w1==1 and w0==1:
        ans+=1
        one=False
    elif w1==1:
        ans+=1
        one=True
    elif not one and w0==1 and w1>1:
        ans+=1
        one=False
    else:
        ans+=2
        one=False

print(ans)