const rl=require("readline").createInterface(process.stdin,process.stdout);

const g=function*(){
	var numMin=10;
	var numMax=1000000001;
	var turn=0;
	for(;;){
		var chkNum=turn==0? 100: 0|(numMin+numMax)/2;
		var chk=yield rl.question(`? ${chkNum}\n`,s=>g.next(s));
		if(chk=="1") numMin=chkNum;
		else if(chk=="-1") numMax=chkNum;
		else{
			console.log(`! ${chkNum+turn}`);
			break;
		}
		if(0<numMin) numMin--;
		numMax--;
		turn++;
	}
	process.exit();
}();
g.next();