Problem:
Score : 100 points

Problem Statement

There are S sheep and W wolves.

If the number of wolves is greater than or equal to that of sheep, the wolves will attack the sheep.

If the wolves will attack the sheep, print unsafe; otherwise, print safe.

Constraints

1 \leq S \leq 100

1 \leq W \leq 100

Input

Input is given from Standard Input in the following format:

S W

Output

If the wolves will attack the sheep, print unsafe; otherwise, print safe.

Sample Input 1

4 5

Sample Output 1

unsafe

There are four sheep and five wolves. The number of wolves is not less than that of sheep, so they will attack them.

Sample Input 2

100 2

Sample Output 2

safe

Many a sheep drive away two wolves.

Sample Input 3

10 10

Sample Output 3

unsafe

Solution in Haskell (GHC 8.8.3) (judge verdict: Runtime Error)

btl :: Int -> Int -> Int -> Int -> String
btl a b c d | c <= 0 ="Yes"
            | a <= 0 = "No"
            | otherwise = btl (a-d) b (c-b) d

main = do
    [a,b,c,d] <- map read <$> (words <$> getLine) :: IO [Int]
    putStrLn (btl a b c d)