use std::io::{BufWriter, Write, read_to_string, stdin, stdout}; const MOD: usize = 1_000_000_007; const N_MAX: usize = 4_000_000; fn get_mod_power(n: usize, p: usize) -> usize { let mut x = p; let mut curr = n % MOD; let mut res = 1; while x > 0 { if x & 1 == 1 { res *= curr; res %= MOD; } x >>= 1; curr *= curr; curr %= MOD; } res } fn main() { let temp = read_to_string(stdin()).unwrap(); let mut iter = temp .split_ascii_whitespace() .map(|x| x.parse::().unwrap()); let m = iter.next().unwrap(); let mut fac = vec![0; N_MAX + 1]; let mut facinv = vec![0; N_MAX + 1]; fac[0] = 1; facinv[0] = 1; fac[1] = 1; facinv[1] = 1; for i in 2..=N_MAX { fac[i] = (fac[i - 1] * i) % MOD; } facinv[N_MAX] = get_mod_power(fac[N_MAX], MOD - 2); for i in (2..N_MAX).rev() { facinv[i] = facinv[i + 1] * (i + 1) % MOD; } let get_nck = |n: usize, k: usize| (fac[n] * facinv[n - k] % MOD) * facinv[k] % MOD; let out = stdout(); let mut writer = BufWriter::new(out.lock()); (0..m).for_each(|_| { let (n, k) = (iter.next().unwrap(), iter.next().unwrap()); write!(writer, "{}\n", get_nck(n, k)).unwrap(); }); }