#include <stdio.h>

int main(void) {
	int ans, result;
	printf("? 100\n"); fflush(stdout);
	scanf("%d", &ans);
	if(ans == 0) {
		result = 100;
	} else if(ans  == -1) {
		int i = 1;
		do {
			printf("? 0\n"); fflush(stdout);
			scanf("%d", &ans);
			i++;
		} while(ans != 0);
		result = i - 1;
	} else {
		int l = 101, r = 1000000000, m = (l + r) / 2, i = 1;
		while(1) {
			printf("? %d\n", m - i); fflush(stdout);
			scanf("%d", &ans);
			if(ans ==  0) { result = m; break; }
			if(ans == +1) { l = m + 1; }
			if(ans == -1) { r = m - 1; }
			m = (l + r) / 2;
			i++;
		}
	}
	printf("! %d\n", result); fflush(stdout);
	return 0;
}