import std.algorithm, std.conv, std.range, std.stdio, std.string;

const maxR = 10 ^^ 9;

void main()
{
  auto r = iota!int(1, maxR+2).assumeSorted!isLow.upperBound(0);
  writeln("! ", r.front); stdout.flush();
}

bool isLow(int _, int x)
{
  writeln("? ", x); stdout.flush();
  auto r = readln.chomp.to!int;
  return r == 0;
}