def xiaochu(s):
l = ''
for i in s:
l = l + i
if len(l)>1 and l[-1]==l[-2]:
l = l[:-2]
return l if l else 0
print(xiaochu(input()))
l = ''
for i in s:
l = l + i
if len(l)>1 and l[-1]==l[-2]:
l = l[:-2]
return l if l else 0
print(xiaochu(input()))