#include <stdio.h>

int main() {
	int top = 1, tail = 1e9, b;
	
	while (1) {
		printf("? %d\n", (top + tail) / 2);
		fflush(stdout);
		scanf("%d", &b);
		if (b) top = (top + tail) / 2;
		else tail = (top + tail) / 2;
		if (top == tail - 1) break;
	}

	printf("! %d\n", top);
	return 0;
}