Problem:
Score : 300 points

Problem Statement

You are playing the following game with Joisino.

Initially, you have a blank sheet of paper.

Joisino announces a number. If that number is written on the sheet, erase the number from the sheet; if not, write the number on the sheet. This process is repeated N times.

Then, you are asked a question: How many numbers are written on the sheet now?

The numbers announced by Joisino are given as A_1, ... ,A_N in the order she announces them. How many numbers will be written on the sheet at the end of the game?

Constraints

1≤N≤100000

1≤A_i≤1000000000(=10^9)

All input values are integers.

Input

Input is given from Standard Input in the following format:

N
A_1
:
A_N

Output

Print how many numbers will be written on the sheet at the end of the game.

Sample Input 1

3
6
2
6

Sample Output 1

1

The game proceeds as follows:

6 is not written on the sheet, so write 6.

2 is not written on the sheet, so write 2.

6 is written on the sheet, so erase 6.

Thus, the sheet contains only 2 in the end. The answer is 1.

Sample Input 2

4
2
5
5
2

Sample Output 2

0

It is possible that no number is written on the sheet in the end.

Sample Input 3

6
12
22
16
22
18
12

Sample Output 3

2

Solution in Rust (1.15.1) (judge verdict: Accepted)

fn main() {
    let stdin = std::io::stdin();
    let mut locked = stdin.lock();
    let mut sc = scanner::Scanner::new(&mut locked);

    let n = sc.next_unsigned() as usize;
    let mut a: Vec<_> = (0..n).map(|_| sc.next_signed()).collect();
    a.sort();
    let mut c = std::collections::BTreeMap::new();
    for x in &a {
        *c.entry(x).or_insert(0) ^= 1;
    }
    let r: usize = c.values().sum();
    println!("{}", r);
}

mod scanner {
    use std::io::{BufRead, Error, ErrorKind, Read};
    use std::str::FromStr;

    pub struct Scanner<'a, R>
    where
        R: 'a + BufRead + ?Sized,
    {
        reader: &'a mut R,
    }

    impl<'a, R> Scanner<'a, R>
    where
        R: 'a + BufRead + ?Sized,
    {
        pub fn new(reader: &'a mut R) -> Self {
            Scanner { reader: reader }
        }

        #[allow(dead_code)]
        pub fn next_byte(&mut self) -> u8 {
            self.reader
                .bytes()
                .skip_while(|ref c| !Self::is_printable(*c.as_ref().ok().unwrap()))
                .next()
                .unwrap()
                .unwrap()
        }

        #[allow(dead_code)]
        pub fn next_bytes(&mut self) -> Vec<u8> {
            self.reader
                .bytes()
                .skip_while(|ref c| !Self::is_printable(*c.as_ref().ok().unwrap()))
                .take_while(|ref c| Self::is_printable(*c.as_ref().ok().unwrap()))
                .collect::<Result<Vec<u8>, _>>()
                .unwrap()
        }

        #[allow(dead_code)]
        pub fn next_unsigned(&mut self) -> u64 {
            self.reader
                .bytes()
                .skip_while(|ref c| !Self::is_printable(*c.as_ref().ok().unwrap()))
                .take_while(|ref c| Self::is_printable(*c.as_ref().ok().unwrap()))
                .fold(Ok(0), |s, x| {
                    s.and_then(|t| {
                        x.and_then(|y| {
                            if b'0' <= y && y <= b'9' {
                                Ok(t * 10 + (y - b'0') as u64)
                            } else {
                                Err(Error::new(ErrorKind::InvalidData, "found not a digit"))
                            }
                        })
                    })
                })
                .unwrap()
        }

        #[allow(dead_code)]
        pub fn next_signed(&mut self) -> i64 {
            self.reader
                .bytes()
                .skip_while(|ref c| !Self::is_printable(*c.as_ref().ok().unwrap()))
                .take_while(|ref c| Self::is_printable(*c.as_ref().ok().unwrap()))
                .fold(Ok([0i64, 0]), |s, x| {
                    x.and_then(|y| {
                        s.and_then(|t| {
                            if t[0] == 0 && y == b'-' {
                                Ok([-1, 0])
                            } else if b'0' <= y && y <= b'9' {
                                Ok([
                                    if t[0] == 0 { 1 } else { t[0] },
                                    t[1] * 10 + (y - b'0') as i64,
                                ])
                            } else {
                                Err(Error::new(ErrorKind::InvalidData, "found not a digit"))
                            }
                        })
                    })
                })
                .and_then(|s| Ok(s[0] * s[1]))
                .unwrap()
        }

        #[allow(dead_code)]
        pub fn next_float(&mut self) -> f64 {
            self.reader
                .bytes()
                .skip_while(|ref c| !Self::is_printable(*c.as_ref().ok().unwrap()))
                .take_while(|ref c| Self::is_printable(*c.as_ref().ok().unwrap()))
                .collect::<Result<Vec<u8>, Error>>()
                .and_then(|t| {
                    String::from_utf8(t).or(Err(Error::new(ErrorKind::InvalidData, "invalid data")))
                })
                .and_then(|s| {
                    f64::from_str(&s).or(Err(Error::new(ErrorKind::InvalidData, "invalid data")))
                })
                .unwrap()
        }

        fn is_printable(c: u8) -> bool {
            0x21 <= c && c <= 0x7e
        }
    }
}