I need to create a method whose arguments are an array of subarrays that are of equal size and a shift value. The output needs to be a new array where the shifted values add up to each other. 

Example 

```
array[[1,2,3,4,5,6],[7,8,9,10,11,12],[13,14,15,16,17,18]]
shift_value = 4

#shift explained below

[1,2,3,4,5,6]
    [7,8,9,10,11,12]
        [13,14,15,16,17,18]

#desired output
[1,2,10,12,27,30,26,28,17,18]

```

Is there a method in ruby to do this? I spent some time making loops finding the index numbers that need to be added and forming a new array, but got lost.