Merkkijono

s=input()+'å'
c=0
for x in range(len(s)//2):
	for j, i in enumerate(s):
		if i==s[j-1] and j!=0:
			c+=1
		elif c>0:
			s=s[:j-1-c]+s[j:]
			break
	c=0
s=s[:len(s)-1]
for i in s:
	if i!=s[0]:
		c=1
		break
if c==0 and len(s)>1:
	s=''
print(s)

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED