S = input()

one = 0
N = len(S)
left = 0
ans = 0
while left < N:
	right = left
	while right < N and S[right] == "1":
		right += 1
	one += right - left
	r = right
	while r < N and S[r] == "0":
		r += 1
	zero = r - right
	
	ans += one // 2 * zero
	one = one // 2 * 2
	left = r
print(ans)