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 Rust (1.42.0) (judge verdict: Wrong Answer)

use input::Input;

fn main() {
    let mut input = Input::new();

    let s: i32 = input.parse();
    let w: i32 = input.parse();

    if s <= w * 2 {
        println!("unsafe");
    } else {
        println!("safe");
    }
}

#[allow(dead_code)]
mod input {
    use std::io::{stdin, BufRead, StdinLock};

    pub struct Input<'a> {
        memory: Vec<String>,
        reader: StdinLock<'a>,
    }

    impl<'a> Input<'a> {
        pub fn new() -> Self {
            Self {
                memory: Vec::new(),
                reader: Box::leak(Box::new(stdin())).lock(),
            }
        }
        pub fn read_line(&mut self) -> String {
            let mut s = String::new();
            self.reader.read_line(&mut s).expect("read_line failed.");
            s
        }
        pub fn parse<T: std::str::FromStr>(&mut self) -> T {
            if self.memory.len() == 0 {
                let s = self.read_line();
                self.memory = s.split_whitespace().map(String::from).rev().collect();
            }
            self.memory.pop().unwrap().parse().ok().unwrap()
        }
    }
}