#P1092. Absolute Difference Equation

    ID: 93 远端评测题 5000ms 128MiB 尝试: 0 已通过: 0 难度: (无) 上传者: 标签>湖南省第十六届大学生计算机程序设计竞赛(HNCPC2020)

Absolute Difference Equation

Description

For a sequence a1, a2, …, an, consider the following operation f: f(a) = {b1, b2, …, bn − 1}, where bi = |ai − ai + 1|.

After applying the operation f for n − 1 times, denoted by fn − 1(a), the sequence will become a single element.

Bobo has a sequence a of length n filled with 0, 1 and ?. He would like to know the number of ways modulo (109 + 7) to replace ? to 0 or 1 such that fn − 1(a) = {1}.

Input

The input consists of several test cases terminated by end-of-file. For each test case:

The first line contains a nonempty string a consisting only of 0, 1 and ?, denoting the given sequence.

  • 1 ≤ |a| ≤ 106
  • The sum of |a| does not exceed 107.

Output

For each test case, print an integer which denotes the result.

1
?????
1010?1?0
1
16
2