import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        new Main().run();
    }

    private void run() {
        Scanner scanner = new Scanner(System.in);
        int S = scanner.nextInt();
        int W = scanner.nextInt();
        if(S <= W) {
            System.out.println("unsafe");
        }else{
            System.out.println("safe");
        }

    }
}