def solution(s):

    end = len(s) - 1

    c = {}
    forward = {}
    backward = {}
    for i in range(len(s) - 1, -1, -1):
        c[s[i]] = c.get(s[i],0) + 1
        backward[i] = c.copy()

    c = {}
    for i in range(0, len(s)):
        c[s[i]] = c.get(s[i],0) + 1
        forward[i] = c.copy()


    window_size = len(s) if len(s) % 2 == 0 else len(s) - 1
    if len(s) % 2 == 0:
        check = forward[end]
        if(len(check) == 2):
            x,y = check.values()
            if x == y:
                return window_size

    everything = forward[end]
    #print(everything)
    #print("WIdnow size : " ,window_size )
    for ws in range(window_size, 0, -2):
        cnt = len(s)-ws+1
        for i in range(0,cnt):
            sp_inc = i
            ep_inc = i+ws
            #print(sp_inc,ep_inc )


            c_forward = False
            c_backward = False
            sp = sp_inc -1
            if sp >= 0:
                c_forward = True
            if ep_inc <= end:
                c_backward = True
                d2 = backward[ep_inc].copy()

            #print(d1,d2,everything)
            result = dict()
            for k,v in everything.items():
                val0 = 0
                val1 = 0
                if c_forward:
                   val0 = forward[sp].get(k,0)
                if c_backward:
                   val1 = backward[ep_inc].get(k,0)
                result[k] = v - val0 - val1

                if(result[k] == 0):
                    del result[k]
            if len(result) == 2:
                x,y = result.values()
                if x == y:
                    #print(result)
                    return ws





    return 0