#include<bits/stdc++.h>
using namespace std;

int main(){
    int lb=0,ub=1e9+1;

    while(ub-lb>1){
        int mid=(ub+lb)/2;
        printf("? %d\n",mid);
        fflush(stdout);

        int res;
        scanf("%d",&res);
        if(res)lb=mid;
        else ub=mid;
    }

    printf("! %d\ ",lb);
    fflush(stdout);
    return 0;
}