import java.util.Scanner
object Main {
  def main(args:Array[String]) = {
    val sc = new java.util.Scanner(System.in)
    val s: Long = sc.nextLong
    val w: Long = sc.nextLong
    
    val diff = s - w
    diff match {
        case ls if ls == 0 => println("unsafe")
        case ls if ls < 0 => println("unsafe")
        case ls if ls > 0 => println("safe")
    }



    
  }
}