#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define df 1
#define step 21
int i=-1;
int s=1000000000;
int a,b;

int ask(){
  printf("? %d\n",s);
  if(df)printf("(i=%d)\n",i);
  fflush(stdout);
  int flag;
  scanf("%d",&flag);
  return flag;
}

void ask2(){
  int c=(a+b)/2-i;
  printf("? %d\n",c);
  if(df)printf("(a,b=%d,%d)\n",a,b);
  fflush(stdout);
  int flag;
  scanf("%d",&flag);
  if(flag>=0) a=c+i;
  if(flag<=0) b=c+i;
}

int main(){
  int ret=-1;
  while(ret==-1){
    i++;
    s/=step;
    s++;
    ret=ask();
  }
  a=s+i; b=s*step+i;

  while(b-a){
    i++;
    ask2();
  }
  printf("! %d\n",a);
  return 0;
}


/// confirm df==0 ///