import java.util.*

fun main(args: Array<String>) {
  val sc = Scanner(System.`in`)
  val s = sc.nextInt()
  val w = sc.nextInt()

  println(abc164a(s, w))
}

private fun abc164a(s: Int, w: Int): String {
  if (s <= w) return "unsafe"
  return "safe"
}
