// yukicoder: No.253 ロウソクの長さ
// 2019.5.10 bal4u

#include <stdio.h>

int x = 1000000;
int answer(int y) {
	int r;
	if (x < y) r = -1;
	else if (x > y) r = 1;
	else if (y == x) r = 0;
	x--;
	return r;
}

int ask(int y) {
	int a;
#if 0
	a = answer(y);
#else
	printf("?%d\n", y), fflush(stdout);
	scanf("%d", &a);
#endif
	return a;
}

int main()
{
	int a, m, l = 0, r = 1000000001;

    while (l < r) {
        m = (l + r) >> 1;
		a = ask(m);
		if (a == 0) { l = m; break; }
        if (a > 0) l = m, r--;
		else {
			if (l > 0) l--;
			r = m-1;
		}
    }
	printf("!%d\n", l), fflush(stdout);
	return 0;
}