#include<bits/stdc++.h>
using namespace std;
int l,r,n,t,m,a,b,k;
int main(){
    cin>>n>>t>>k;
    for(l=1,r=n;l<=r;){
        m=(l+r)/2;
        cout<<"?"<<l<<""<<m<<endl;
        cout.flush();
        cin>>a;
        b=m-l+1-a;
        if(b<k){
            k-=b;
            l=m+1;
        }else r=m-1;
    }
    cout<<"!"<<l;
    return 0;
}