Build a growable list from scratch

Build a list that grows as values are added, the way the built-in growable lists work inside. Store the values in a fixed-size block of slots; when the block is full, make a new block with more room and copy the values across. Do not use a ready-made growable list.

Your function receives a list of commands and runs them in order on an empty list. Positions count from 0.

• "add x" puts the value x at the end;
• "get i" outputs the value at position i;
• "remove i" removes the value at position i, outputs it, and moves every later value one place forward;
• "size" outputs how many values the list holds.

If position i does not exist, "get i" and "remove i" output -1 and change nothing. Return all outputs, in order. The hidden tests check the results and the speed: a block that grows by one slot on every add is too slow for 300,000 commands.