#include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
using namespace std;
int l, r, mid, x;
int main() {
    l = 1;
    r = 1e9;
    while (l <= r) {
        mid = (l + r) >> 1;
        cout << mid << endl;
        fflush(stdout);
        cin >> x;
        if (x == 0)
            return 0;
        if (x == -1)
            l = mid + 1;
        else
            r = mid - 1;
    }
    /*cout<<r<<endl; //注意二分的出口
    fflush(stdout);
    return 0;
    */
}