module main;
// インタラクティブ問題、二分探索
import std;

void main()
{
	int l = 1, r = 10 ^^ 9 + 1;
	while (r - l > 1) {
		int m = (l + r) / 2;
		writefln("? %d", m);
		stdout.flush;
		int ret = readln.chomp.to!int;
		if (ret == 1)
			l = m;
		else
			r = m;
	}
	writefln("! %d", l);
	stdout.flush;
}