// ---------- begin ModInt ----------
const MOD: u32 = 1_000_000_007;

#[derive(Clone, Copy)]
struct ModInt(u32);

impl std::ops::Add for ModInt {
    type Output = ModInt;
    fn add(self, rhs: ModInt) -> Self::Output {
        let mut d = self.0 + rhs.0;
        if d >= MOD {
            d -= MOD;
        }
        ModInt(d)
    }
}

impl std::ops::AddAssign for ModInt {
    fn add_assign(&mut self, rhs: ModInt) {
        *self = *self + rhs;
    }
}

impl std::ops::Sub for ModInt {
    type Output = ModInt;
    fn sub(self, rhs: ModInt) -> Self::Output {
        let mut d = self.0 + MOD - rhs.0;
        if d >= MOD {
            d -= MOD;
        }
        ModInt(d)
    }
}

impl std::ops::SubAssign for ModInt {
    fn sub_assign(&mut self, rhs: ModInt) {
        *self = *self - rhs;
    }
}

impl std::ops::Mul for ModInt {
    type Output = ModInt;
    fn mul(self, rhs: ModInt) -> Self::Output {
        ModInt((self.0 as u64 * rhs.0 as u64 % MOD as u64) as u32)
    }
}

impl std::ops::MulAssign for ModInt {
    fn mul_assign(&mut self, rhs: ModInt) {
        *self = *self * rhs;
    }
}

impl std::ops::Neg for ModInt {
    type Output = ModInt;
    fn neg(self) -> Self::Output {
        ModInt(if self.0 == 0 {0} else {MOD - self.0})
    }
}

impl std::fmt::Display for ModInt {
    fn fmt<'a>(&self, f: &mut std::fmt::Formatter<'a>) -> std::fmt::Result {
        write!(f, "{}", self.0)
    }
}

impl std::str::FromStr for ModInt {
    type Err = std::num::ParseIntError;
    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let val = s.parse::<u32>()?;
        Ok(ModInt::new(val))
    }
}

impl From<usize> for ModInt {
    fn from(val: usize) -> ModInt {
        ModInt((val % MOD as usize) as u32)
    }
}

impl From<i64> for ModInt {
    fn from(val: i64) -> ModInt {
        let m = MOD as i64;
        ModInt::new((val % m + m) as u32)
    }
}

#[allow(dead_code)]
impl ModInt {
    pub fn new(n: u32) -> ModInt {
        ModInt(n % MOD)
    }
    pub fn zero() -> ModInt {
        ModInt(0)
    }
    pub fn one() -> ModInt {
        ModInt(1)
    }
    pub fn pow(self, mut n: u32) -> ModInt {
        let mut t = ModInt::one();
        let mut s = self;
        while n > 0 {
            if n & 1 == 1 {
                t *= s;
            }
            s *= s;
            n >>= 1;
        }
        t
    }
    pub fn inv(self) -> ModInt {
        assert!(self.0 > 0);
        self.pow(MOD - 2)
    }
}
// ---------- end ModInt ----------
// ---------- begin Precalc ----------
#[allow(dead_code)]
struct Precalc {
    inv: Vec<ModInt>,
    fact: Vec<ModInt>,
    ifact: Vec<ModInt>,
}

#[allow(dead_code)]
impl Precalc {
    pub fn new(n: usize) -> Precalc {
        let mut inv = vec![ModInt::one(); n + 1];
        let mut fact = vec![ModInt::one(); n + 1];
        let mut ifact = vec![ModInt::one(); n + 1];
        for i in 2..(n + 1) {
            fact[i] = fact[i - 1] * ModInt(i as u32);
        }
        ifact[n] = fact[n].inv();
        if n > 0 {
            inv[n] = ifact[n] * fact[n - 1];
        }
        for i in (1..n).rev() {
            ifact[i] = ifact[i + 1] * ModInt((i + 1) as u32);
            inv[i] = ifact[i] * fact[i - 1];
        }
        Precalc {
            inv: inv,
            fact: fact,
            ifact: ifact,
        }
    }
    pub fn inv(&self, n: usize) -> ModInt {
        assert!(n > 0);
        self.inv[n]
    }
    pub fn fact(&self, n: usize) -> ModInt {
        self.fact[n]
    }
    pub fn ifact(&self, n: usize) -> ModInt {
        self.ifact[n]
    }
    pub fn comb(&self, n: usize, k: usize) -> ModInt {
        if k > n {
            return ModInt::zero();
        }
        self.fact[n] * self.ifact[k] * self.ifact[n - k]
    }
}
// ---------- end Precalc ----------
// ---------- begin Scanner(require delimiter) ----------
mod scanner {
    use std;
    pub struct Scanner<R> {
        reader: R,
        buf: Vec<u8>,
    }
    #[allow(dead_code)]
    impl<R: std::io::BufRead> Scanner<R> {
        pub fn new(reader: R) -> Self {
            Scanner {
                reader: reader,
                buf: Vec::with_capacity(1024),
            }
        }
        fn read(&mut self, del: u8) {
            self.buf.clear();
            self.reader.read_until(del, &mut self.buf).ok();
            assert!(self.buf.pop().unwrap() == del);
        }
        pub fn next<T: std::str::FromStr>(&mut self, del: u8) -> T {
            self.read(del);
            std::str::from_utf8(&self.buf)
                .unwrap()
                .trim()
                .parse::<T>()
                .ok()
                .unwrap()
        }
        pub fn next_bytes(&mut self, del: u8) -> Vec<u8> {
            self.read(del);
            std::str::from_utf8(&self.buf)
                .unwrap()
                .trim()
                .bytes()
                .collect()
        }
    }
}
// ---------- end scanner(require delimiter) ----------

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

fn run<R: std::io::BufRead>(sc: &mut scanner::Scanner<R>) {
    let n: usize = sc.next(b'\n');
    let m = 2000;
    let mut g = vec![vec![]; m + 1];
    for _ in 0..n {
        let a: usize = sc.next(b' ');
        let b: usize = sc.next(b'\n');
        g[a].push(b);
    }
    let mut dp = vec![ModInt::zero(); 2 * m + 1];
    for g in g.iter().rev() {
        for b in g.iter() {
            dp[m - *b] += ModInt::one();
        }
        let mut prev = ModInt::zero();
        for v in dp.iter_mut() {
            *v += prev;
            prev = *v;
        }
    }
    let mut ans = ModInt::zero();
    for g in g.iter().skip(1) {
        let mut prev = ModInt::zero();
        for v in dp.iter_mut() {
            *v += prev;
            prev = *v;
        }
        for b in g.iter() {
            ans += dp[m + *b];
        }
    }
    let pc = Precalc::new(8 * m);
    for (a, g) in g.iter().enumerate() {
        for b in g.iter() {
            ans -= pc.comb(2 * a + 2 * b, 2 * a);
        }
    }
    ans *= pc.inv(2);
    println!("{}", ans);
}


Measured memory_bytes: 6396