Solve the programming task below in a Python markdown code block.
Recently, Greg got a grid with n rows and m columns. Rows are indexed from 1 to n and columns are indexed from 1 to m. The cell $ ( i , j )$ is the cell of intersection of row i and column j. Each cell has a number written on it. The number written on cell  $( i , j )$  is equal to  $(i+j)$.  
Now, Greg wants to select some cells from the grid, such that for every pair of  selected cells ,the numbers on the cells are co-prime.  Determine the maximum number of cells that Greg can select.

------ Input  ------ 

Single line containing  integers n and m denoting number of rows and number of columns respectively.

------ Output ------ 

Single line containing the answer.

------ Constraints ------ 

$$1 ≤ n,m ≤ 10^{6}$$

----- Sample Input 1 ------ 
3 4

----- Sample Output 1 ------ 
4