S = input()

now = 1
tmp = 0
cnt = 0
if S[0] == "1":
	tmp += 1
ans = 0
while now < len(S):
	if S[now] == "1":
		if S[now-1] == "0":
			ans += (tmp // 2) * cnt
			tmp = (tmp // 2) * 2
		tmp += 1
	else:
		if S[now-1] == "1":
			cnt = 1
		else:
			cnt += 1
	
	now += 1

if S[-1] == "0":
    ans += (tmp // 2) * cnt

print(ans)