Merkkijono

def f_b(s):
    for b in range(len(s)- 1):
        if s[b]== s[b+ 1]:
            return b
    return -1

def f_e(s, b):
    e= b
    for i in range(b, len(s)- 1):
        if s[i]== s[i+ 1]:
            e+= 1
        else:
            break
    return e

def f(s):
    b= 0
    while len(s)> 0:
        b= f_b(s)
        if 0> b:
            return s
        e= f_e(s, b)
        s= s[:b]+ s[e+ 1:]
    return s

if __name__ == "__main__":
#    print('<'+ f('CAACCB')+ '>')
#    print('---')
#    print('<'+ f('ABCDDCBA')+ '>')
#    print('---')
#    print('<'+ f('ABCDEEEDCBAA')+ '>')
    print(f(input()))

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