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# Expected number of Segments

Problem Description

Find the expected value of the number of segments in a string of length A in a language having alphabet size B.

A segment in defined as maximum contiguous substring containing the same character. E.g. In string 10011, the segments are 1, 00 and 11. The number of segments will be 3.

Problem Constraints

1 <= A,B <= 109

Input Format

The first argument contains an integer A, denoting the length of the string.

The second argument contains an integer B, denoting the alphabet size.

Output Format

Return the expected value of the number of segments. This can be represented in the form of x/y. Return  x.y-1 (mod 109 + 7 ).

Example Input

Input 1:

``` A = 1
B = 2
```

Input 2:

```  A = 2
B = 2
```

Example Output

Output 1:

```  1
```

Output 2:

```  500000005
```

Example Explanation

Explanation 1:

```  The length is 1. So there will only be 1 segment.
```

Explanation 2:

```  There are 4 cases-

00-1 segment
01-2 segments
10-2 segments
11-1 segment

Hence, the expected number of segments is 6/4.
```

NOTE: You only need to implement the given function. Do not read input, instead use the arguments to the function. Do not print the output, instead return values as specified. Still have a question? Checkout Sample Codes for more details.
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