1520F1 · Guess the K-th Zero (Easy version)

Problem: This is an interactive problem.

This is an easy version of the problem. The difference from the hard version is that in the easy version $t=1$ and the number of queries is limited to $20$.

Polycarp is playing a computer game. In this game, an array consisting of zeros and ones is hidden. Polycarp wins if he guesses the position of the $k$-th zero from the left $t$ times.

Polycarp can make no more than $20$ requests of the following type:

• ? $l$ $r$ — find out the sum of all elements in positions from $l$ to $r$ ($1 \le l \le r \le n$) inclusive.

In this (easy version) of the problem, this paragraph doesn't really make sense since $t=1$ always. To make the game more interesting, each guessed zero turns into one and the game continues on the changed array. More formally, if the position of the $k$-th zero was $x$, then after Polycarp guesses this position, the $x$-th element of the array will be replaced from $0$ to $1$. Of course, this feature affects something only for $t>1$.

Help Polycarp win the game.

Note: In the first test, the $[1, 0, 1, 1, 0, 1]$ array is hidden. In this test $k=2$.