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 r = acio::Reader::from_stdin();
    let n: usize = r.read();
    let m: usize = r.read();
    let h: Vec<u64> = r.read_by(n);
    let mut gh = vec![true; n];
    for _ in 0..m {
        let a: usize = r.read();
        let b: usize = r.read();
        let (a, b) = (a - 1, b - 1);
        if h[a] == h[b] {
            gh[a] = false;
            gh[b] = false;
        } else if h[a] < h[b] {
            gh[a] = false;
        } else {
            gh[b] = false;
        }
    }
    let mut c = 0;
    for g in gh {
        if g {
            c += 1;
        }
    }
    println!("{}", c);
}

//-- MODULES --

/// Mathematics Module
#[allow(dead_code)]
mod math {
    use std::mem::swap;

    /// Methods for Each Integer Type
    pub trait Integer {}
    /// Implements trait Integer
    macro_rules! integer {
        ($t:ty) => {
            impl Integer for $t {
                // NOTHING...
            }
        };
    }

    /// Methods for Each Natural Integer Type
    pub trait Natural {
        fn lcm(v1: Self, v2: Self) -> Self;
        fn gcd(v1: Self, v2: Self) -> Self;
    }
    /// Implements trait Natural
    macro_rules! natural {
        ($t:ty) => {
            impl Natural for $t {
                fn lcm(v1: $t, v2: $t) -> $t {
                    v1 * v2 / Self::gcd(v1, v2)
                }

                fn gcd(v1: $t, v2: $t) -> $t {
                    let (mut v1, mut v2) = (v1, v2);
                    if v1 < v2 {
                        swap(&mut v1, &mut v2);
                    }
                    while v2 != 0 {
                        let t = v1;
                        v1 = v2;
                        v2 = t % v2;
                    }
                    return v1;
                }
            }
        };
    }

    // BEGIN DECLARATIONS
    integer!(i8);
    integer!(i16);
    integer!(i32);
    integer!(i64);
    integer!(isize);
    integer!(u8);
    integer!(u16);
    integer!(u32);
    integer!(u64);
    integer!(usize);
    // ---
    natural!(u8);
    natural!(u16);
    natural!(u32);
    natural!(u64);
    natural!(usize);
    // END DECLARATIONS
}

/// IO Module for AtCoder
#[allow(dead_code)]
mod acio {
    use std::fmt::Debug;
    use std::io::{stdin, BufRead, BufReader, Read, Stdin};
    use std::str::FromStr;

    /// Multi-Purpose Value Reader
    pub struct Reader<R>
    where
        R: Read,
    {
        input: BufReader<R>,
        stack: Vec<String>,
    }

    impl<R: Read> Reader<R> {
        /// Create Reader from Read
        pub fn new<T>(input: R) -> Self {
            // Self { // <- Warning: NOT YET on AtCoder
            Reader {
                input: BufReader::new(input),
                stack: vec![],
            }
        }

        /// Read Multiple Value
        pub fn read_by<F>(&mut self, count: usize) -> Vec<F>
        where
            F: FromStr,
            <F as FromStr>::Err: Debug,
        {
            (0..count).map(|_| self.read()).collect()
        }

        /// Read Single Value
        pub fn read<F>(&mut self) -> F
        where
            F: FromStr,
            <F as FromStr>::Err: Debug,
        {
            while self.stack.is_empty() {
                let mut line = self.read_line();
                self.stack.append(&mut line);
                self.stack.reverse();
            }
            self.stack.pop().unwrap().parse().unwrap()
        }

        /// Read Space Split Line
        fn read_line(&mut self) -> Vec<String> {
            let mut buf = String::new();
            self.input.read_line(&mut buf).unwrap();
            buf.split_whitespace().map(|s| s.to_string()).collect()
        }
    }

    impl Reader<Stdin> {
        /// Create Reader from stdin
        pub fn from_stdin() -> Self {
            Self::new::<Reader<Stdin>>(stdin())
        }
    }

    /*
    impl<T> Drop for Reader<T> {
        /// FOR DEBUG
        fn drop(&mut self) {
            if self.stack.len() != 0 {
                panic!("Reader with remaining value is dropped.")
            }
        }
    }
    */
}