Zalando Manipulation

The string contains only A, B, C, D. You may repeatedly delete two adjacent characters that are A/B or C/D, in either order. Output any result that cannot be reduced further.

输入格式

One line with a string of length 0..250000, containing only A, B, C, D.

输出格式

Output any irreducible string; for an empty result, output an empty line.

样例 1

输入：

CBACD

输出：

C

样例 2

输入：

CABABD

输出：

样例 3

输入：

ACBDACBD

输出：

ACBDACBD