#[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 { (source = $s:expr, $($r:tt)*) => { let mut iter = $s.split_whitespace(); let mut next = || { iter.next().unwrap() }; input_inner!{next, $($r)*} }; ($($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, chars) => { read_value!($next, String).chars().collect::>() }; ($next:expr, usize1) => { read_value!($next, usize) - 1 }; ($next:expr, [ $t:tt ]) => {{ let len = read_value!($next, usize); (0..len).map(|_| read_value!($next, $t)).collect::>() }}; ($next:expr, $t:ty) => { $next().parse::<$t>().expect("Parse error") }; } /// Verified by: https://beta.atcoder.jp/contests/arc099/submissions/3515280 mod mod_int { use std::ops::*; pub trait Mod: Copy + Clone { fn m() -> i64; } #[derive(Copy, Clone, Hash, PartialEq, Eq, PartialOrd, Ord)] pub struct ModInt { pub x: i64, phantom: ::std::marker::PhantomData<*const M> } impl ModInt { fn check_integrity(self) { debug_assert!(self.x >= 0); debug_assert!(self.x < M::m()); } // 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 } } #[allow(dead_code)] pub fn mul_fast(self, other: Self) -> Self { self.check_integrity(); other.check_integrity(); ModInt::new_internal(self.x * other.x % M::m()) } #[allow(dead_code)] pub fn mul_slow(self, other: Self) -> Self { // Naive multiplication in order to avoid overflow self.check_integrity(); other.check_integrity(); let mut sum = ModInt::new_internal(0); let mut cur = self; let mut e = other.x; if self.x < other.x { cur = other; e = self.x; } while e > 0 { if e % 2 == 1 { sum += cur; } cur += cur; e /= 2; } sum } pub fn pow(self, mut e: i64) -> Self { self.check_integrity(); 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: Self) -> Self { self.check_integrity(); other.check_integrity(); 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: Self) -> Self { self.check_integrity(); other.check_integrity(); 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: Self) -> Self { self.mul_fast(other) } } impl AddAssign for ModInt { fn add_assign(&mut self, other: Self) { *self = *self + other; } } impl SubAssign for ModInt { fn sub_assign(&mut self, other: Self) { *self = *self - other; } } impl MulAssign for ModInt { fn mul_assign(&mut self, other: Self) { *self = *self * other; } } 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 { self.x.fmt(f) } } } // 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 ModInt = mod_int::ModInt

; fn med(a: usize, b: usize, c: usize) -> usize { let mut b = vec![a, b, c]; b.sort(); b[1] } fn dfs(n: usize, v: usize, b: &mut Vec, hs: &mut HashSet>) { if v >= n { let mut a = vec![0; n]; for i in 0 .. n { let mut tmp = 0; for j in 0 .. i + 1 { tmp = med(tmp, b[j], n - 1 - i + j); } a[i] = tmp; } hs.insert(a); return; } for i in 0 .. n { b.push(i); dfs(n, v + 1, b, hs); b.pop(); } } fn brute(n: usize) { let mut hs: HashSet> = HashSet::new(); dfs(n, 0, &mut Vec::new(), &mut hs); println!("size = {}", hs.len()); let mut last = vec![0; n]; let mut cut = HashSet::new(); let mut targ = HashSet::new(); for mut v in hs { last[v[n - 1]] += 1; let mut hit = false; if v[2] == 3 && v[3] == 2 { targ.insert(v[0 .. 4].to_vec()); hit = true; } if v[n - 1] == 1 { println!(" {:?} {}", v, if hit { "hit" } else { "" }); v.pop(); cut.insert(v); } } eprintln!("last = {:?}", last); for c in targ { eprintln!(" targ {:?}", c); } } fn solve() { let out = std::io::stdout(); let mut out = BufWriter::new(out.lock()); macro_rules! puts { ($format:expr) => (write!(out,$format).unwrap()); ($format:expr, $($args:expr),+) => (write!(out,$format,$($args),*).unwrap()) } input! { n: usize, } // brute(n); let mut dp = vec![vec![ModInt::new(0); n]; n + 1]; let mut dp2 = vec![vec![ModInt::new(0); n]; n + 1]; dp[0][0] = ModInt::new(1); for i in 1 .. n + 1 { let mut cur = ModInt::new(0); for j in 0 .. n { cur += dp[i - 1][j]; // eprintln!("i = {}, j = {}, cur = {}", i, j, cur); dp[i][j] += cur; cur += dp2[i - 1][j]; } for j in 0 .. n - 1 { let turn = n - 1 - j; if i >= turn { dp2[i][j] += dp[i - turn][j + 1] + dp2[i - 1][j + 1]; dp2[i][j] += dp2[i - 1][j]; } } } if false { for i in 0 .. n + 1 { eprintln!("dp[{}] = {:?}", i, dp[i]); eprintln!("dp2[{}] = {:?}", i, dp2[i]); } } let mut tot = ModInt::new(0); for i in 0 .. n { tot += dp2[n][i] + dp[n][i]; } puts!("{}\n", 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(); }