#include<stdio.h>

int main(void){
int x=1;
int y=1000000000;

while(x<y){
int m=(x+y)/2;
printf("? %d\n",m);
int ans;
scanf("%d",&ans);
if(ans){
x=m;
} else {
y=m;
}
}
printf("! %d\n",x);
return 0;
}