# Problem B

0-1 Sequences

You are given a sequence, in the form of a string with
characters ‘`0`’, ‘`1`’, and ‘`?`’ only.
Suppose there are $k$
‘`?`’s. Then there are $2^ k$ ways to replace each
‘`?`’ by a ‘`0`’ or a ‘`1`’, giving
$2^ k$ different 0-1
sequences (0-1 sequences are sequences with only zeroes and
ones).

For each 0-1 sequence, define its number of inversions as
the minimum number of adjacent swaps required to sort the
sequence in non-decreasing order. In this problem, the sequence
is sorted in non-decreasing order precisely when all the zeroes
occur before all the ones. For example, the sequence `11010` has $5$ inversions. We can sort it by the
following moves: `11010` $\rightarrow $ `11001` $\rightarrow $ `10101` $\rightarrow $ `01101` $\rightarrow $ `01011` $\rightarrow $ `00111`.

Find the sum of the number of inversions of the $2^ k$ sequences, modulo $1\, 000\, 000\, 007$ ($10^9 + 7$).

## Input

The first and only line of input contains the input string,
consisting of characters ‘`0`’,
‘`1`’, and ‘`?`’ only, and the input string has between
$1$ to $500\, 000$ characters, inclusive.

## Output

Output an integer indicating the aforementioned number of inversions modulo $1\, 000\, 000\, 007$.

Sample Input 1 | Sample Output 1 |
---|---|

?0? |
3 |