Merkkijono

s = list(input())
while len(s) > 1:
    p, l, c = 0, 0, ''
    mp, ml = 0, 0
    for i, d in enumerate(s):
        if d == c:
            l += 1
        else:
            c = d
            p = i
            l = 1
        if l > ml:
            mp = p
            ml = l
    if ml == 1:
        break
    del s[mp:mp+ml]
print(''.join(s) if len(s) else None)

Test 1

Verdict: ACCEPTED

Test 2

Verdict: WRONG ANSWER

Test 3

Verdict: WRONG ANSWER

Test 4

Verdict: WRONG ANSWER

Test 5

Verdict: WRONG ANSWER

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED