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)

fn main() {
    let mut line = String::new();
    let stdin = std::io::stdin();
    let _ = stdin.read_line(&mut line);
    let n = line.split_whitespace().nth(0).unwrap().parse::<usize>().unwrap();
    line.clear();
    let mut towers = vec![true; n];
    let _ = stdin.read_line(&mut line);
    let hs: Vec<_> = line.split_whitespace().map(|x| x.parse::<usize>().unwrap()).collect();
    line.clear();
    while let Ok(l) = stdin.read_line(&mut line) {
        if l <= 0 { break; }
        let ab: Vec<_> = line.split_whitespace().map(|x| x.parse::<usize>().unwrap()-1).collect();
        line.clear();
        if hs[ab[0]] <= hs[ab[1]] { towers[ab[0]] = false; }
        if hs[ab[0]] >= hs[ab[1]] { towers[ab[1]] = false; }
    }
    println!("{}", towers.iter().filter(|&x| *x).count());
}