#include <stdio.h>

int main(){
	int numMin=1;
	int numMax=1000000001;
	for(;;){
		int chkNum=(numMin+numMax)/2;
		printf("? %d\n",chkNum);
		int v; scanf("%d",&v);
		if(v==1) numMin=chkNum; else numMax=chkNum;
		if(numMin==numMax-1){
			printf("! %d\n",numMin);
			break;
		}
	}
	return 0;
}