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## 1057. Amount of Degrees

Time limit: 1.0 second
Memory limit: 64 MB
Create a code to determine the amount of integers, lying in the set [X; Y] and being a sum of exactly K different integer degrees of the integer B.
Example. Let X = 15, Y = 20, K = 2, B = 2. By this example three integers are the sum of exactly two integer degrees of number 2:
17 = 24 + 20,
18 = 24 + 21,
20 = 24 + 22.

### Input

The first line contains integers X and Y (1 ≤ X ≤ Y ≤ 231 − 1). The next two lines contain integers K and B (1 ≤ K ≤ 20; 2 ≤ B ≤ 10).

### Output

Output the amount of integers, lying between X and Y, being a sum of exactly K different integer degrees of B.

### Sample

inputoutput
```15 20
2
2
```
```3
```
Problem Source: Rybinsk State Avia Academy
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