#include<bits/stdc++.h>
main(){
    int min = 0,max = 100000000;
    while(min!=max){
        printf("? %d\n",(min+max+1)/2);
        fflush(stdout);
        int ans;
        scanf("%d",&ans);
        if(ans){
            min = (min+max+1)/2;
        }else{
            max = (min+max-1)/2;
        }
    }
    printf("! %d\n",min);
    fflush(stdout);
}