Problem:
Score: 400 points

Problem Statement

In Takahashi Kingdom, there is a east-west railroad and N cities along it, numbered 1, 2, 3, ..., N from west to east.
A company called AtCoder Express possesses M trains, and the train i runs from City L_i to City R_i (it is possible that L_i = R_i).
Takahashi the king is interested in the following Q matters:

The number of the trains that runs strictly within the section from City p_i to City q_i, that is, the number of trains j such that p_i \leq L_j and R_j \leq q_i.

Although he is genius, this is too much data to process by himself. Find the answer for each of these Q queries to help him.

Constraints

N is an integer between 1 and 500 (inclusive).

M is an integer between 1 and 200 \ 000 (inclusive).

Q is an integer between 1 and 100 \ 000 (inclusive).

1 \leq L_i \leq R_i \leq N (1 \leq i \leq M)

1 \leq p_i \leq q_i \leq N (1 \leq i \leq Q)

Input

Input is given from Standard Input in the following format:

N M Q
L_1 R_1
L_2 R_2
:
L_M R_M
p_1 q_1
p_2 q_2
:
p_Q q_Q

Output

Print Q lines. The i-th line should contain the number of the trains that runs strictly within the section from City p_i to City q_i.

Sample Input 1

2 3 1
1 1
1 2
2 2
1 2

Sample Output 1

3

As all the trains runs within the section from City 1 to City 2, the answer to the only query is 3.

Sample Input 2

10 3 2
1 5
2 8
7 10
1 7
3 10

Sample Output 2

1
1

The first query is on the section from City 1 to 7. There is only one train that runs strictly within that section: Train 1.
The second query is on the section from City 3 to 10. There is only one train that runs strictly within that section: Train 3.

Sample Input 3

10 10 10
1 6
2 9
4 5
4 7
4 7
5 8
6 6
6 7
7 9
10 10
1 8
1 9
1 10
2 8
2 9
2 10
3 8
3 9
3 10
1 10

Sample Output 3

7
9
10
6
8
9
6
7
8
10

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

use std::io::*;
use std::str::*;
use std::collections::*;

pub fn read_from<T: FromStr, R: Read>(s: &mut R) -> T {
    let s = s.bytes().map(|c| c.unwrap() as char)
        .skip_while(|c| c.is_whitespace())
        .take_while(|c| !c.is_whitespace())
        .collect::<String>();
    if !s.is_empty() {
        if let Ok(s) = s.parse::<T>() {
            s
        } else {
            panic!("faild to parse {}", s);
        }
    } else {
        if cfg!(local) {
            // eprintln!("reached to EOF");
        }
        std::process::exit(0)
    }
}

pub fn read<T: FromStr>() -> T {
    let stdin = stdin();
    let mut stdin = stdin.lock();
    read_from(&mut stdin)
}

pub fn chars() -> Vec<char> {
    let stdin = stdin();
    let mut stdin = stdin.lock();
    let s: String = read_from(&mut stdin);
    s.chars().collect()
}

pub fn readn<T: FromStr>(n: usize) -> Vec<T> {
    let stdin = stdin();
    let mut stdin = stdin.lock();
    (0..n).map(|_| read_from(&mut stdin)).collect()
}

fn calc(c: char) -> usize {
    if c == '1' {
        1
    } else {
        2e18 as usize
    }
}

fn main() {
    loop {
        let n: usize = read();
        let m: usize = read();
        let q: usize = read();

        let mut to_l: Vec<_> = vec![BTreeSet::new(); n + 1];
        let mut to_r: Vec<_> = vec![BTreeSet::new(); n + 1];
        let mut rails: Vec<(usize, usize, usize)> = (0..m).map(|i| (read(), read(), i)).collect();
        rails.sort();
        let mut rails: VecDeque<_> = rails.iter().cloned().collect();
        for &(l, r, i)in rails.iter() {
            to_l[r].insert((l, i));
            to_r[l].insert((r, i));
        }
        let mut qs: Vec<_> = (0..q).map(|i| {
            let l: usize = read();
            let r: usize = read();
            (l, r, i)
        }).collect();
        qs.sort();

        let mut ans = vec![0; q];
        for &(ql, qr, i) in qs.iter() {
            while rails.len() > 0 && rails.front().unwrap().0 < ql {
                let (l, r, i) = rails.pop_front().unwrap();
                to_l[r].remove(&(l, i));
                to_r[l].remove(&(r, i));
            }
            let mut cnt = 0;
            for r in ql..qr + 1 {
                cnt += to_l[r].len();
            }
            ans[i] = cnt;
        }

        for e in ans.iter() {
            println!("{}", e);
        }
    }
}