import collections,sys,math,functools,operator,itertools,bisect,heapq,decimal,string,time,random
#sys.setrecursionlimit(10**9)
#sys.set_int_max_str_digits(0)
#input = sys.stdin.readline
#n = int(input())
#alist = list(map(int,input().split()))
#alist = []
s = list(input().rstrip())
#n,m = map(int,input().split())
#for i in range(n):
#    alist.append(list(map(int,input().split())))
ans = 0
def rle(seq):
    res = []
    for i in seq:
        if not res or res[-1][0] != i:
            res.append([i,1])
        else:
            res[-1][-1] += 1
    return res
t = rle(s)
p = 0

for i,j in reversed(t):
    if i == '0':
        p += j
    else:
        ans += p * (j//2)

print(ans)