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

int main() {
    int l = 0, r = 1e9 + 9;
    while(r - l > 1) {
            int mid = (r+l)/2;
            cout << mid << endl;
            char c; cin >> c;
            if(c == 0) r = mid;
            else if(c == 1) l = mid;
            else return 0;
    }
    cout << l << endl;
    return 0;
}