func readInts() -> [Int] {
    return readLine()!.split(separator: " ").map { Int($0)! }
}

func main() {
    let line = readInts()
    let s = line[0]
    let w = line[1]
    
    if s <= w {
        print("unsafe")
    } else {
        print("safe")
    }
}

main()
