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 Ruby (2.7.1) (judge verdict: Runtime Error)

a_hp,a_at,b_hp,b_at = gets.chomp.split.map &:to_i

cnt = 1
a_flg = 0
b_flg = 0

while a_hp <= 0 || b_hp <= 0
  b_hp -= a_at if cnt.odd?
  a_flg = 1 if b_hp <= 0
  a_hp -= b_at if cnt.even?
  b_flg = 1 if a_hp <= 0
  cnt += 1
end

if a_flg
  print 'Yes'
else
  print 'No'
end