Hackerrank - Strange Grid Again Solution

A strange grid has been recovered from an old book. It has  columns and infinite number of rows. The bottom row is considered as the first row. First few rows of the grid are like this:

..............

..............

20 22 24 26 28

11 13 15 17 19

10 12 14 16 18

 1  3  5  7  9

 0  2  4  6  8

The grid grows upwards forever!

Your task is to find the integer in ^th column in ^th row of the grid.

Input Format

There will be two integers r and c separated by a single space.

Constraints

Rows are indexed from bottom to top and columns are indexed from left to right.

Output Format

Output the answer in a single line.

Sample Input

6 3

Sample Output

25

Explanation

The number in the 6^th row and 3^rd column is 25.

def strangeGrid(r, c):
    d,m = divmod(r-1,2)
    a = d*10+2*c
    a -= 1 if m else 2
    return a

r,c = map(int,input().split())
print(strangeGrid(r, c))