#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define df 0
int a=1,b=1000000000;

void ask(){
  int c=(a+b)/2;
  printf("? %d\n",c);
  int flag;
  scanf("%d",&flag);
  if(flag) a=c;
  else b=c;
}

int main(){
  while(b-a>1){
    ask();
  }
  printf("! %d\n",a);
  return 0;
}


/// confirm df==0 ///