fn main() { input! { n: usize, p: u32, } type M = ModInt; StaticMod::set_modulo(p); let sieve = Sieve::new(n); let mut divisor = vec![]; let pc = precalc::Precalc::new(n); let mut dp = vec![M::zero(); n + 1]; let mut imos = vec![M::zero(); n + 1]; for i in 3..=n { sieve.factorize(i, &mut divisor); imos[i] = imos[i] + imos[i - 1]; dp[i] += imos[i]; dp[i] = (M::one() + dp[i] * pc.inv(i)) * pc.inv(i - divisor.len()) * M::from(i); let v = dp[i]; for &d in divisor.iter() { let q = i / d; imos[q * d] += v; let r = (q + 1) * d; if r <= n { imos[r] -= v; } } dp[i] = v; } println!("{}", dp[n]); } use modint::*; // ---------- 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, $t)).collect::>() }; ($iter:expr, chars) => { read_value!($iter, String).chars().collect::>() }; ($iter:expr, bytes) => { read_value!($iter, String).bytes().collect::>() }; ($iter:expr, usize1) => { read_value!($iter, usize) - 1 }; ($iter:expr, $t:ty) => { $iter.next().unwrap().parse::<$t>().expect("Parse error") }; } // ---------- end input macro ---------- mod util { pub trait Join { fn join(self, sep: &str) -> String; } impl Join for I where I: Iterator, T: std::fmt::Display, { fn join(self, sep: &str) -> String { let mut s = String::new(); use std::fmt::*; for (i, v) in self.enumerate() { if i > 0 { write!(&mut s, "{}", sep).ok(); } write!(&mut s, "{}", v).ok(); } s } } } mod modint { use std::marker::*; use std::ops::*; pub trait Modulo { fn modulo() -> u32; fn im() -> u64; fn reduce(z: u64) -> u32 { let x = (z as u128 * Self::im() as u128 >> 64) as u32; let mut v = z as u32 - x * Self::modulo(); if v >= Self::modulo() { v += Self::modulo(); } v } } pub struct StaticMod; static mut STATIC_MOD: u32 = 0; static mut STATIC_MOD_IM: u64 = 0; impl Modulo for StaticMod { fn modulo() -> u32 { unsafe { STATIC_MOD } } fn im() -> u64 { unsafe { STATIC_MOD_IM } } } #[allow(dead_code)] impl StaticMod { pub fn set_modulo(p: u32) { unsafe { STATIC_MOD = p; STATIC_MOD_IM = (!0u64 / p as u64) + 1; } } } pub struct ModInt(u32, PhantomData); impl Clone for ModInt { fn clone(&self) -> Self { ModInt::build(self.0) } } impl Copy for ModInt {} impl Add for ModInt { type Output = ModInt; fn add(self, rhs: Self) -> Self::Output { let mut d = self.0 + rhs.0; if d >= T::modulo() { d -= T::modulo(); } Self::build(d) } } impl AddAssign for ModInt { fn add_assign(&mut self, rhs: Self) { *self = *self + rhs; } } impl Sub for ModInt { type Output = ModInt; fn sub(self, rhs: Self) -> Self::Output { let mut d = self.0 - rhs.0; if self.0 < rhs.0 { d += T::modulo(); } Self::build(d) } } impl SubAssign for ModInt { fn sub_assign(&mut self, rhs: Self) { *self = *self - rhs; } } impl Mul for ModInt { type Output = ModInt; fn mul(self, rhs: Self) -> Self::Output { Self::build(T::reduce(self.0 as u64 * rhs.0 as u64)) } } impl MulAssign for ModInt { fn mul_assign(&mut self, rhs: Self) { *self = *self * rhs; } } impl Neg for ModInt { type Output = ModInt; fn neg(self) -> Self::Output { if self.0 == 0 { Self::zero() } else { Self::build(T::modulo() - self.0) } } } impl std::fmt::Display for ModInt { fn fmt<'a>(&self, f: &mut std::fmt::Formatter<'a>) -> std::fmt::Result { write!(f, "{}", self.get()) } } impl std::fmt::Debug for ModInt { fn fmt<'a>(&self, f: &mut std::fmt::Formatter<'a>) -> std::fmt::Result { write!(f, "{}", self.get()) } } impl Default for ModInt { fn default() -> Self { Self::zero() } } impl std::str::FromStr for ModInt { type Err = std::num::ParseIntError; fn from_str(s: &str) -> Result { let val = s.parse::()?; Ok(ModInt::new(val)) } } impl From for ModInt { fn from(val: usize) -> ModInt { ModInt::new_unchecked((val % T::modulo() as usize) as u32) } } impl From for ModInt { fn from(val: u64) -> ModInt { ModInt::new_unchecked((val % T::modulo() as u64) as u32) } } impl From for ModInt { fn from(val: i64) -> ModInt { let m = T::modulo() as i64; ModInt::new((val % m + m) as u32) } } #[allow(dead_code)] impl ModInt { fn build(d: u32) -> Self { ModInt(d, PhantomData) } pub fn zero() -> Self { Self::build(0) } pub fn is_zero(&self) -> bool { self.0 == 0 } } #[allow(dead_code)] impl ModInt { pub fn new_unchecked(d: u32) -> Self { Self::build(d) } pub fn new(d: u32) -> Self { Self::new_unchecked(d % T::modulo()) } pub fn one() -> Self { Self::new_unchecked(1) } pub fn get(&self) -> u32 { self.0 } pub fn pow(&self, mut n: u64) -> Self { let mut t = Self::one(); let mut s = *self; while n > 0 { if n & 1 == 1 { t *= s; } s *= s; n >>= 1; } t } pub fn inv(&self) -> Self { assert!(!self.is_zero()); self.pow((T::modulo() - 2) as u64) } } } // ---------- end ModInt ---------- // ---------- begin Precalc ---------- mod precalc { use super::modint::*; #[allow(dead_code)] pub struct Precalc { inv: Vec>, fact: Vec>, ifact: Vec>, } #[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::new_unchecked(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::new_unchecked((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 perm(&self, n: usize, k: usize) -> ModInt { if k > n { return ModInt::zero(); } self.fact[n] * self.ifact[n - k] } 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 ---------- use modint::*; type M = ModInt; use std::ops::*; pub trait Zero: Sized + Add { fn zero() -> Self; } pub fn zero() -> T { T::zero() } impl Zero for ModInt { fn zero() -> Self { Self::zero() } } impl Zero for usize { fn zero() -> Self { 0 } } pub trait ArrayAdd { type Item; fn add(&self, rhs: &[Self::Item]) -> Vec; } impl ArrayAdd for [T] where T: Zero + Copy, { type Item = T; fn add(&self, rhs: &[Self::Item]) -> Vec { let mut c = vec![T::zero(); self.len().max(rhs.len())]; c[..self.len()].copy_from_slice(self); c.add_assign(rhs); c } } pub trait ArrayAddAssign { type Item; fn add_assign(&mut self, rhs: &[Self::Item]); } impl ArrayAddAssign for [T] where T: Add + Copy, { type Item = T; fn add_assign(&mut self, rhs: &[Self::Item]) { assert!(self.len() >= rhs.len()); self.iter_mut().zip(rhs).for_each(|(x, a)| *x = *x + *a); } } impl ArrayAddAssign for Vec where T: Zero + Add + Copy, { type Item = T; fn add_assign(&mut self, rhs: &[Self::Item]) { if self.len() < rhs.len() { self.resize(rhs.len(), T::zero()); } self.as_mut_slice().add_assign(rhs); } } pub trait ArraySub { type Item; fn sub(&self, rhs: &[Self::Item]) -> Vec; } impl ArraySub for [T] where T: Zero + Sub + Copy, { type Item = T; fn sub(&self, rhs: &[Self::Item]) -> Vec { let mut c = vec![T::zero(); self.len().max(rhs.len())]; c[..self.len()].copy_from_slice(self); c.sub_assign(rhs); c } } pub trait ArraySubAssign { type Item; fn sub_assign(&mut self, rhs: &[Self::Item]); } impl ArraySubAssign for [T] where T: Sub + Copy, { type Item = T; fn sub_assign(&mut self, rhs: &[Self::Item]) { assert!(self.len() >= rhs.len()); self.iter_mut().zip(rhs).for_each(|(x, a)| *x = *x - *a); } } impl ArraySubAssign for Vec where T: Zero + Sub + Copy, { type Item = T; fn sub_assign(&mut self, rhs: &[Self::Item]) { if self.len() < rhs.len() { self.resize(rhs.len(), T::zero()); } self.as_mut_slice().sub_assign(rhs); } } pub trait ArrayDot { type Item; fn dot(&self, rhs: &[Self::Item]) -> Vec; } impl ArrayDot for [T] where T: Mul + Copy, { type Item = T; fn dot(&self, rhs: &[Self::Item]) -> Vec { assert!(self.len() == rhs.len()); self.iter().zip(rhs).map(|p| *p.0 * *p.1).collect() } } pub trait ArrayDotAssign { type Item; fn dot_assign(&mut self, rhs: &[Self::Item]); } impl ArrayDotAssign for [T] where T: MulAssign + Copy, { type Item = T; fn dot_assign(&mut self, rhs: &[Self::Item]) { assert!(self.len() == rhs.len()); self.iter_mut().zip(rhs).for_each(|(x, a)| *x *= *a); } } pub trait ArrayMul { type Item; fn mul(&self, rhs: &[Self::Item]) -> Vec; } impl ArrayMul for [T] where T: Zero + Mul + Copy, { type Item = T; fn mul(&self, rhs: &[Self::Item]) -> Vec { if self.is_empty() || rhs.is_empty() { return vec![]; } let mut res = vec![zero(); self.len() + rhs.len() - 1]; for (i, a) in self.iter().enumerate() { for (c, b) in res[i..].iter_mut().zip(rhs) { *c = *c + *a * *b; } } res } } // --------- end sieve ---------- pub struct Sieve { size: usize, factor: Vec, } impl Sieve { pub fn new(size: usize) -> Sieve { let mut factor = (0..(size + 1)).collect::>(); for i in (2..).take_while(|p| p * p <= size) { if i == factor[i] { for j in i..(size / i + 1) { factor[j * i] = i; } } } Sieve { size: size, factor: factor, } } pub fn factor(&self, n: usize) -> Option { assert!(n <= self.size); if n == 1 { None } else { Some(self.factor[n]) } } pub fn factorize(&self, mut n: usize, res: &mut Vec) { assert!(n <= self.size); res.clear(); res.push(1); while let Some(p) = self.factor(n) { let len = res.len(); while n % p == 0 { n /= p; for _ in 0..len { let v = res[res.len() - len] * p; res.push(v); } } } } } // --------- end sieve ----------