Problem:
Score : 300 points

Problem Statement

There are N observatories in AtCoder Hill, called Obs. 1, Obs. 2, ..., Obs. N. The elevation of Obs. i is H_i.
There are also M roads, each connecting two different observatories. Road j connects Obs. A_j and Obs. B_j.

Obs. i is said to be good when its elevation is higher than those of all observatories that can be reached from Obs. i using just one road.
Note that Obs. i is also good when no observatory can be reached from Obs. i using just one road.

How many good observatories are there?

Constraints

2 \leq N \leq 10^5

1 \leq M \leq 10^5

1 \leq H_i \leq 10^9

1 \leq A_i,B_i \leq N

A_i \neq B_i

Multiple roads may connect the same pair of observatories.

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N M
H_1 H_2 ... H_N
A_1 B_1
A_2 B_2
:
A_M B_M

Output

Print the number of good observatories.

Sample Input 1

4 3
1 2 3 4
1 3
2 3
2 4

Sample Output 1

2

From Obs. 1, you can reach Obs. 3 using just one road. The elevation of Obs. 1 is not higher than that of Obs. 3, so Obs. 1 is not good.

From Obs. 2, you can reach Obs. 3 and 4 using just one road. The elevation of Obs. 2 is not higher than that of Obs. 3, so Obs. 2 is not good.

From Obs. 3, you can reach Obs. 1 and 2 using just one road. The elevation of Obs. 3 is higher than those of Obs. 1 and 2, so Obs. 3 is good.

From Obs. 4, you can reach Obs. 2 using just one road. The elevation of Obs. 4 is higher than that of Obs. 2, so Obs. 4 is good.

Thus, the good observatories are Obs. 3 and 4, so there are two good observatories.

Sample Input 2

6 5
8 6 9 1 2 1
1 3
4 2
4 3
4 6
4 6

Sample Output 2

3

Solution in Rust (1.42.0) (judge verdict: Accepted)

use input::{Input, ReadMode};

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

    let n = input.parse();
    let m = input.parse();
    let h = (0..n).map(|_| input.parse()).collect::<Vec<u64>>();
    let mut v = vec![Vec::new(); n];

    for _ in 0..m {
        let a: usize = input.parse();
        let b: usize = input.parse();
        v[a - 1].push(b - 1);
        v[b - 1].push(a - 1);
    }

    let mut ans = 0;
    for i in 0..n {
        let x = &h[i];
        let mut ok = true;
        for j in v[i].iter() {
            if x <= &h[*j] {
                ok = false;
                break;
            }
        }
        if ok {
            ans += 1;
        }
    }

    println!("{}", ans);
}

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

    pub enum ReadMode {
        Full,
        Line,
    }

    pub struct Input<'a> {
        lock: std::io::StdinLock<'static>,
        iter: Option<std::str::SplitAsciiWhitespace<'a>>,
        mode: ReadMode,
    }

    impl<'a> Input<'a> {
        fn naive_read(&mut self) -> Option<std::str::SplitAsciiWhitespace<'a>> {
            let mut s = Box::leak(Box::new(String::new()));
            let res = match self.mode {
                ReadMode::Full => self.lock.read_to_string(&mut s),
                ReadMode::Line => self.lock.read_line(&mut s),
            };
            res.ok().expect("failed to read");
            Some(s.split_ascii_whitespace())
        }
        pub fn new(mode: ReadMode) -> Self {
            let lock = Box::leak(Box::new(std::io::stdin())).lock();
            let iter = None;
            Self { lock, iter, mode }
        }
        pub fn read_line(&mut self) -> String {
            let mut s = String::new();
            self.lock.read_line(&mut s).ok().expect("failed to read");
            s
        }
        pub fn parse<T: std::str::FromStr>(&mut self) -> T {
            match &mut self.iter {
                Some(iter) => {
                    let x = match iter.next() {
                        Some(x) => x,
                        None => {
                            self.iter = self.naive_read();
                            self.iter.as_mut().unwrap().next().expect("reached EOF")
                        }
                    };
                    x.parse().ok().expect("failed to parse")
                }
                None => {
                    self.iter = self.naive_read();
                    self.parse()
                }
            }
        }
    }
}