|시간 제한||메모리 제한||제출||정답||맞은 사람||정답 비율|
|0.3 초 (추가 시간 없음)||256 MB||33||11||7||35.000%|
Write a program that guesses an integer X in the range 1, . . . , N.
This is an interactive task. When your program starts, the first line of input contains the integer N (1 ≤ N ≤ 109). The value of X is kept secret by the grading system.
Then your program can issue queries by writing them to the output in the form “? P”, where P is an integer (1 ≤ P ≤ N). The grading system writes the response in the next line of the input. The response is −1 if P < X, 0 if P = X, and 1 if P > X. Your program may issue at most 50 queries in each test case.
When your program wants to guess the number X, it should output “= X” (1 ≤ X ≤ N) and terminate. The grading system will not respond to this output and will not accept further queries after that.
5 -1 1 0
? 1 ? 3 ? 2 = 2