I have a loop that produces multiple lists such as these:

```
  [1,6,2,8,3,4]

  [8,1,2,3,7,2]

  [9,2,5,6,1,4]

```

*For each list, I want to subtract the first two elements, and then use that value to then subtract the third element from.* 

For example, the first list should end up looking like:

```
  [-5, 4,-6, 5,-1]

```

I have tried to manually do this, but there are too many lists to do this and it would take too much time. 

How would I do that in the least amount of lines of code?