import java.lang.IllegalArgumentException


fun ask(value: Int): Response {
    println("? $value")
    return Response(readLine()!!)
}
sealed class Response{
    companion object {
        operator fun invoke(word: String): Response {
            return when(word.trim()) {
                "out" -> Out
                "safe" -> Safe
                else -> throw IllegalArgumentException()
            }
        }
    }
}
object Out : Response()
object Safe : Response()
fun main() {
    var min = 0
    var max = 1001
    while (min < max) {
        val mid = (min + max) shr 1
        when(ask(mid)) {
            Out -> when(ask(mid + 1)) {
                Out -> max = mid
                Safe -> min = mid + 1
            }
            Safe -> min = mid + 1
        }
    }
    println("! ${max - 1}")
}