n = '0'+input()
N = []
for i in range(len(n)):
    N.append(n[len(n)-1-i])
n = N
#print(n)
#exit()
ans = 0
ln = len(n)
oc = 0
zc = 0
for i in range(ln):
    if n[i] == "1":
        if i == ln-1:
            ans += 1
        elif n[i+1] == "0":
            ans += 1
            n[i] = "0"
        else:
            while n[i] == "1":
                n[i] = "0"
                i += 1
                #print(i,n[i])
            n[i] = "1"
            i -= 1
            ans += 1
print(ans)