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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 B.
Example. Let X=15, Y=20, K=2, B=2. By this example 3 numbers are the sum of exactly two integer degrees of number 2:
17 = 24+20,
18 = 24+21,
20 = 24+22.

### Input

The first line of input contains integers X and Y, separated with a space (1 ≤ X ≤ Y ≤ 231−1). The next two lines contain integers K and B (1 ≤ K ≤ 20; 2 ≤ B ≤ 10).

### Output

Output should contain a single integer — 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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