#include<stdio.h>

typedef long long int ln;

int main(void){

ln low=1;
ln high=1000000000;

while(low+1<high){
 ln m=(low+high)/2;
 printf("? %lld\n",m);
fflush(stdin);
 int ans;
 scanf("%d",&ans);
 if(ans){
  low=m;
 } else {
  high=m;
 }
}
if(high==low){
printf("! %lld\n",low);
return 0;
}
printf("? %lld\n",high);
fflush(stdin);

int ans;
scanf("%d",ans);
if(ans){
printf("! %lld\n",high);
} else {
printf("! %lld\n",low);
}
return 0;
}