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: Time Limit Exceeded)

use std::io::*;
use std::str::FromStr;

fn read<T: FromStr>() -> T {
    let stdin = stdin();
    let stdin = stdin.lock();
    let token: String = stdin
        .bytes()
        .map(|c| c.expect("failed to read char") as char) 
        .skip_while(|c| c.is_whitespace())
        .take_while(|c| !c.is_whitespace())
        .collect();
    token.parse().ok().expect("failed to parse token")
}

//use std::collections::VecDeque;

fn main() {
    let n: usize = read();
    let m: usize = read();
    let h: Vec<usize> = (0..n).map(|_| read()).collect();
   
    //let mut rinsetsu: Vec<VecDeque<usize>> = vec![VecDeque::new(); n];
    let mut a: Vec<usize> = Vec::new();
    let mut b: Vec<usize> = Vec::new();
    for _ in 0..m {
        let ai: usize = read();
        let bi: usize = read();
        a.push(ai-1);
        b.push(bi-1);
    }

    let mut ans: usize = 0;
    let mut c: Vec<bool> = vec![true; n];

    'outer: for i in 0..n {
        if !c[i] {
            continue;
        }
        ans += 1;
        for j in 0..m {
            if a[j] == i {
                if h[i] > h[b[j]] {
                    c[b[j]] = false;
                } else if h[i] == h[b[j]] {
                    c[i] = false;
                    c[b[j]] = false;
                    ans -= 1;
                    continue 'outer;
                } else {
                    c[i] = false;
                    ans -= 1;
                    continue 'outer;
                }
            } else if b[j] == i {
                if h[i] > h[a[j]] {
                    c[a[j]] = false;
                } else if h[i] == h[a[j]] {
                    c[i] = false;
                    c[a[j]] = false;
                    ans -= 1;
                    continue 'outer;
                } else {
                    c[i] = false;
                    ans -= 1;
                    continue 'outer;
                }
            }
        }
    }

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