fn main() { input! { n: usize, m: usize, } let k = n.max(m); let mut a = vec![0; k + 1]; let mut b = vec![0; k + 1]; a[1..=n].fill(1); b[1..=m].fill(1); zeta(&mut a); zeta(&mut b); for (a, b) in a.iter_mut().zip(b) { *a *= b; } izeta(&mut a); println!("{}", a[1]); } fn zeta(a: &mut [i64]) { let n = a.len() - 1; enumerate_prime(n, |p| { for j in (1..(n / p + 1)).rev() { a[j] += a[j * p]; } }); } fn izeta(a: &mut [i64]) { let n = a.len() - 1; enumerate_prime(n, |p| { for j in 1..(n / p + 1) { a[j] -= a[j * p]; } }); } // ---------- 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 ---------- // ---------- begin enumerate prime ---------- fn enumerate_prime(n: usize, mut f: F) where F: FnMut(usize), { assert!(1 <= n && n <= 5 * 10usize.pow(8)); let batch = (n as f64).sqrt().ceil() as usize; let mut is_prime = vec![true; batch + 1]; for i in (2..).take_while(|p| p * p <= batch) { if is_prime[i] { let mut j = i * i; while let Some(p) = is_prime.get_mut(j) { *p = false; j += i; } } } let mut prime = vec![]; for (i, p) in is_prime.iter().enumerate().skip(2) { if *p && i <= n { f(i); prime.push(i); } } let mut l = batch + 1; while l <= n { let r = std::cmp::min(l + batch, n + 1); is_prime.clear(); is_prime.resize(r - l, true); for &p in prime.iter() { let mut j = (l + p - 1) / p * p - l; while let Some(is_prime) = is_prime.get_mut(j) { *is_prime = false; j += p; } } for (i, _) in is_prime.iter().enumerate().filter(|p| *p.1) { f(i + l); } l += batch; } } // ---------- end enumerate prime ----------