# Find Water In Glass

medium

1. Pepcoder arranged some glasses in the form of pascal triangle. 2. Capacity of each glass is 1 litre. If you pour K amount of water in a glass, it will retain 1 litre and rest of it gets equally distributed in left bottom glass and right bottom glass. 3. If pepcoder pours K litres of water in the topmost glass, you have to find out the amount of water in Cth glass of Rth row. Assumption -> There are enough glasses in the triangle till no glass overflows.

## Constraints

1 <= K <= 500 1 <= R,C <= K

## Format

### Input

A number K representing amount of water poured in topmost glass. Two numbers R and C

### Output

A number representing the amount of water present in Cth glass of Rth row.

## Example

Sample Input

3
1
0

### Sample Output

1.0