#include <iostream>
#include <iomanip>

typedef long long ll;

int main(void)
{
  std::cin.tie(0);
  std::ios::sync_with_stdio(false);
  std::cout << std::fixed << std::setprecision(8);
  ll bottom = 0, top = 1000000001;
  ll piv = (bottom + top) / 2;
  while (top - bottom > 1) {
    std::cout << "? " << piv << std::endl; std::cout.flush();
    int ans;
    std::cin >> ans;
    if (ans == 1) bottom = piv;
    else top = piv;
    piv = (top + bottom) / 2;
  }
  std::cout << "! " << bottom << std::endl;
  return 0;
}