Mnbvcxzlkjhgfdsapoiuytrewqwertyuiopasdfghjklzxcvbnm

So first half = rev(bottom) + rev(middle) + rev(top) = mnbvcxz + lkjhgfdsa + poiuytrewq = exactly positions 1–26 (since 7+9+10=26). And indeed that matches given string start: mnbvcxzlkjhgfdsapoiuytrewq — check: after mnbvcxz comes lkjhgfdsa — yes, then poiuytrewq — yes.

: In digital linguistics, strings like these are often used as "keyboard smashes" to express intense emotion (excitement, frustration, or "keysmashing") where words fail. mnbvcxzlkjhgfdsapoiuytrewqwertyuiopasdfghjklzxcvbnm