def query(x)
  STDOUT.puts("? #{x}")
  STDOUT.flush
  gets.chomp
end

ok = 0
ng = 1001

while (ok - ng).abs >= 2
  x = (ok + ng) / 2
  ret = query(x)

  if ret == 'safe'
    ok = x
  else
    ret2 = query(x + 1)

    if ret2 == 'safe'
      ok = x + 1
    else
      ng = x
    end
  end
end

puts "! #{ok}"