#include <stdio.h>

int main(void)
{
	int c = 1000000000, l = 0, n, t, s = 0;
	while (1) {
		n = (c - l) / 2 + l;
		if (n == s) n++;
		s = n;
		printf("? %d\n", n);
		fflush(0);
		scanf("%d", &t);
		if (t) l = n;
		else c = n - 1;
		if (c == l) {
			printf("! %d\n", c);
			fflush(0);
			break;
		}
	}
	return 0;
}