#[allow(unused_imports)] use std::cmp::*; #[allow(unused_imports)] use std::collections::*; use std::io::{Write, BufWriter}; // https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8 macro_rules! input { ($($r:tt)*) => { let stdin = std::io::stdin(); let mut bytes = std::io::Read::bytes(std::io::BufReader::new(stdin.lock())); let mut next = move || -> String{ bytes.by_ref().map(|r|r.unwrap() as char) .skip_while(|c|c.is_whitespace()) .take_while(|c|!c.is_whitespace()) .collect() }; input_inner!{next, $($r)*} }; } macro_rules! input_inner { ($next:expr) => {}; ($next:expr,) => {}; ($next:expr, $var:ident : $t:tt $($r:tt)*) => { let $var = read_value!($next, $t); input_inner!{$next $($r)*} }; } macro_rules! read_value { ($next:expr, ( $($t:tt),* )) => { ($(read_value!($next, $t)),*) }; ($next:expr, [ $t:tt ; $len:expr ]) => { (0..$len).map(|_| read_value!($next, $t)).collect::>() }; ($next:expr, $t:ty) => ($next().parse::<$t>().expect("Parse error")); } /// Verified by https://atcoder.jp/contests/abc198/submissions/21774342 mod mod_int { use std::ops::*; pub trait Mod: Copy { fn m() -> i64; } #[derive(Copy, Clone, Hash, PartialEq, Eq, PartialOrd, Ord)] pub struct ModInt { pub x: i64, phantom: ::std::marker::PhantomData } impl ModInt { // x >= 0 pub fn new(x: i64) -> Self { ModInt::new_internal(x % M::m()) } fn new_internal(x: i64) -> Self { ModInt { x: x, phantom: ::std::marker::PhantomData } } pub fn pow(self, mut e: i64) -> Self { debug_assert!(e >= 0); let mut sum = ModInt::new_internal(1); let mut cur = self; while e > 0 { if e % 2 != 0 { sum *= cur; } cur *= cur; e /= 2; } sum } #[allow(dead_code)] pub fn inv(self) -> Self { self.pow(M::m() - 2) } } impl>> Add for ModInt { type Output = Self; fn add(self, other: T) -> Self { let other = other.into(); let mut sum = self.x + other.x; if sum >= M::m() { sum -= M::m(); } ModInt::new_internal(sum) } } impl>> Sub for ModInt { type Output = Self; fn sub(self, other: T) -> Self { let other = other.into(); let mut sum = self.x - other.x; if sum < 0 { sum += M::m(); } ModInt::new_internal(sum) } } impl>> Mul for ModInt { type Output = Self; fn mul(self, other: T) -> Self { ModInt::new(self.x * other.into().x % M::m()) } } impl>> AddAssign for ModInt { fn add_assign(&mut self, other: T) { *self = *self + other; } } impl>> SubAssign for ModInt { fn sub_assign(&mut self, other: T) { *self = *self - other; } } impl>> MulAssign for ModInt { fn mul_assign(&mut self, other: T) { *self = *self * other; } } impl Neg for ModInt { type Output = Self; fn neg(self) -> Self { ModInt::new(0) - self } } impl ::std::fmt::Display for ModInt { fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result { self.x.fmt(f) } } impl ::std::fmt::Debug for ModInt { fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result { let (mut a, mut b, _) = red(self.x, M::m()); if b < 0 { a = -a; b = -b; } write!(f, "{}/{}", a, b) } } impl From for ModInt { fn from(x: i64) -> Self { Self::new(x) } } // Finds the simplest fraction x/y congruent to r mod p. // The return value (x, y, z) satisfies x = y * r + z * p. fn red(r: i64, p: i64) -> (i64, i64, i64) { if r.abs() <= 10000 { return (r, 1, 0); } let mut nxt_r = p % r; let mut q = p / r; if 2 * nxt_r >= r { nxt_r -= r; q += 1; } if 2 * nxt_r <= -r { nxt_r += r; q -= 1; } let (x, z, y) = red(nxt_r, r); (x, y - q * z, z) } } // mod mod_int macro_rules! define_mod { ($struct_name: ident, $modulo: expr) => { #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)] struct $struct_name {} impl mod_int::Mod for $struct_name { fn m() -> i64 { $modulo } } } } const MOD: i64 = 1_000_000_007; define_mod!(P, MOD); type MInt = mod_int::ModInt

; // https://judge.yosupo.jp/submission/5155 mod pollard_rho { /// binary gcd pub fn gcd(mut x: i64, mut y: i64) -> i64 { if y == 0 { return x; } if x == 0 { return y; } let k = (x | y).trailing_zeros(); y >>= k; x >>= x.trailing_zeros(); while y != 0 { y >>= y.trailing_zeros(); if x > y { let t = x; x = y; y = t; } y -= x; } x << k } fn add_mod(x: i64, y: i64, n: i64) -> i64 { let z = x + y; if z >= n { z - n } else { z } } fn mul_mod(x: i64, mut y: i64, n: i64) -> i64 { assert!(x >= 0); assert!(x < n); let mut sum = 0; let mut cur = x; while y > 0 { if (y & 1) == 1 { sum = add_mod(sum, cur, n); } cur = add_mod(cur, cur, n); y >>= 1; } sum } fn mod_pow(x: i64, mut e: i64, n: i64) -> i64 { let mut prod = if n == 1 { 0 } else { 1 }; let mut cur = x % n; while e > 0 { if (e & 1) == 1 { prod = mul_mod(prod, cur, n); } e >>= 1; if e > 0 { cur = mul_mod(cur, cur, n); } } prod } pub fn is_prime(n: i64) -> bool { if n <= 1 { return false; } let small = [2, 3, 5, 7, 11, 13]; if small.iter().any(|&u| u == n) { return true; } if small.iter().any(|&u| n % u == 0) { return false; } let mut d = n - 1; let e = d.trailing_zeros(); d >>= e; // https://miller-rabin.appspot.com/ let a = [2, 325, 9375, 28178, 450775, 9780504, 1795265022]; a.iter().all(|&a| { if a % n == 0 { return true; } let mut x = mod_pow(a, d, n); if x == 1 { return true; } for _ in 0..e { if x == n - 1 { return true; } x = mul_mod(x, x, n); if x == 1 { return false; } } x == 1 }) } fn pollard_rho(n: i64, c: &mut i64) -> i64 { // An improvement with Brent's cycle detection algorithm is performed. // https://maths-people.anu.edu.au/~brent/pub/pub051.html if n % 2 == 0 { return 2; } loop { let mut x: i64; // tortoise let mut y = 2; // hare let mut d = 1; let cc = *c; let f = |i| add_mod(mul_mod(i, i, n), cc, n); let mut r = 1; // We don't perform the gcd-once-in-a-while optimization // because the plain gcd-every-time algorithm appears to // outperform, at least on judge.yosupo.jp :) while d == 1 { x = y; for _ in 0..r { y = f(y); d = gcd((x - y).abs(), n); if d != 1 { break; } } r *= 2; } if d == n { *c += 1; continue; } return d; } } /// Outputs (p, e) in p's ascending order. pub fn factorize(x: i64) -> Vec<(i64, usize)> { if x <= 1 { return vec![]; } let mut hm = std::collections::HashMap::new(); let mut pool = vec![x]; let mut c = 1; while let Some(u) = pool.pop() { if is_prime(u) { *hm.entry(u).or_insert(0) += 1; continue; } let p = pollard_rho(u, &mut c); pool.push(p); pool.push(u / p); } let mut v: Vec<_> = hm.into_iter().collect(); v.sort(); v } } // mod pollard_rho trait Change { fn chmax(&mut self, x: Self); fn chmin(&mut self, x: Self); } impl Change for T { fn chmax(&mut self, x: T) { if *self < x { *self = x; } } fn chmin(&mut self, x: T) { if *self > x { *self = x; } } } fn dfs(pe: &[(i64, usize)], idx: usize, c: i64, rem: i64, phi: i64) -> MInt { if idx >= pe.len() { return MInt::new(c).pow(2 * rem) * phi; } let mut tot = dfs(pe, idx + 1, c, rem, phi); let (p, e) = pe[idx]; let mut phi = phi * (p - 1); let mut rem = rem / p; for _ in 1..e + 1 { tot += dfs(pe, idx + 1, c, rem, phi); rem /= p; phi *= p; } tot } fn main() { // In order to avoid potential stack overflow, spawn a new thread. let stack_size = 104_857_600; // 100 MB let thd = std::thread::Builder::new().stack_size(stack_size); thd.spawn(|| solve()).unwrap().join().unwrap(); } fn solve() { input! { t: usize, nc: [(i64, i64); t], } for (n, c) in nc { let pe = pollard_rho::factorize(n); let mut tot = MInt::new(c).pow(n) * n; tot += dfs(&pe, 0, c, n, 1); tot *= MInt::new(2 * n).inv(); println!("{}", tot); } }