I am stuck in a problem. I want to update my cartesian index.

I have a matrix (`x`) 200x6 that is binary. 1 if assigned, 0 otherwise. I want to find the cartesian index of when `x` is 1 in the first 3 columns and in the last 3 elements.

I have the following code:

```
index_right = findall( x -> x == 1, sol.x_assignment[:,1:3])
index_left = findall( x -> x == 1, sol.x_assignment[:,4:6])
index_left

```

However `index_right` is correct, `index_left` is wrong as it returns index between 1,2,3 instead of 4,5,6

```
CartesianIndex(2, 1)
CartesianIndex(3, 1)
CartesianIndex(10, 2)
CartesianIndex(11, 1)

```

Expected output:

```
CartesianIndex(2, 4)
CartesianIndex(3, 4)
CartesianIndex(10, 5)
CartesianIndex(11, 4)

```

How can I update `index_left` to add +3 in the second index for all?