use std::collections::*;
use std::io::Write;

type Map<K, V> = BTreeMap<K, V>;
type Set<T> = BTreeSet<T>;
type Deque<T> = VecDeque<T>;

fn main() {
    input! {
        n: usize,
        p: [(usize, usize); n],
    }
    let mut p = p;
    for p in p.iter_mut() {
        p.0 += 2 * n;
        p.1 += 2 * n;
    }
    p.sort_by_key(|p| p.0);
    let s = (0..n).map(|i| p[i].0 - i).max().unwrap();
    p.sort_by_key(|p| p.1);
    let t = (0..n).map(|i| p[i].1 - i).min().unwrap();
    if t < s {
        println!("0");
        return;
    }
    let mut ans = t - s + 1;
    if t - s <= 100 {
        ans = 0;
        let mut ok = |k: usize| -> bool {
            p.sort_by_key(|p| p.0);
            let mut h = BinaryHeap::new();
            let mut x = 0;
            for i in 0..n {
                while x < n && p[x].0 <= s + i {
                    h.push(!p[x].1);
                    x += 1;
                }
                let v = !h.pop().unwrap();
                if v < s + i {
                    return false;
                }
            }
            true
        };
        ans = (s..=t).filter(|k| ok(*k)).count();
    }
    println!("{}", ans);
}

// ---------- begin input macro ----------
// reference: https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8
#[macro_export]
macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
    ($($r:tt)*) => {
        let s = {
            use std::io::Read;
            let mut s = String::new();
            std::io::stdin().read_to_string(&mut s).unwrap();
            s
        };
        let mut iter = s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
}

#[macro_export]
macro_rules! input_inner {
    ($iter:expr) => {};
    ($iter:expr, ) => {};
    ($iter:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($iter, $t);
        input_inner!{$iter $($r)*}
    };
}

#[macro_export]
macro_rules! read_value {
    ($iter:expr, ( $($t:tt),* )) => {
        ( $(read_value!($iter, $t)),* )
    };
    ($iter:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($iter, $t)).collect::<Vec<_>>()
    };
    ($iter:expr, chars) => {
        read_value!($iter, String).chars().collect::<Vec<char>>()
    };
    ($iter:expr, bytes) => {
        read_value!($iter, String).bytes().collect::<Vec<u8>>()
    };
    ($iter:expr, usize1) => {
        read_value!($iter, usize) - 1
    };
    ($iter:expr, $t:ty) => {
        $iter.next().unwrap().parse::<$t>().expect("Parse error")
    };
}
// ---------- end input macro ----------