#include <string.h>
#include <stdio.h>

int main(void){
	int low=0, high = 1000000000;
	
	while( low < high){
		int mid = (low+high)/2;
		int ret;
		printf("? %d\n", mid);
		fflush(stdin);
		scanf("%d", &ret);
		
		if(ret == 1){
			high = mid;
		}
		
		if( ret == 0){
			low = mid+1;
		}
		
	}
	
	fflush(stdin);
	
	printf("! %d\n", low);
	return 0;
}