题解 | #点击消除#

stack = []
s = input()
for i in s:
    if len(stack) == 0:
        stack.append(i)
    else:
        if stack[-1] == i:
            stack.pop()
        else:
            stack.append(i)
if len(stack) == 0:
    print("0")
else:
    for i in stack:
        print(i,end='')