#include<stdio.h>
int main()
{
	int min, mid, max;
	min = 0;
	max = 1000000009;
	int res;
	while (max - min > 1)
	{
		mid = (max + min) / 2;
		printf("? %d\n", mid);
		fflush(stdout);
		scanf("%d", &res);
		if (res > 0)
			min = mid;
		else
			max = mid;
	}
	printf("! %d\n", min);
}