use std::io::Read; fn get_word() -> String { let stdin = std::io::stdin(); let mut stdin=stdin.lock(); let mut u8b: [u8; 1] = [0]; loop { let mut buf: Vec = Vec::with_capacity(16); loop { let res = stdin.read(&mut u8b); if res.unwrap_or(0) == 0 || u8b[0] <= b' ' { break; } else { buf.push(u8b[0]); } } if buf.len() >= 1 { let ret = String::from_utf8(buf).unwrap(); return ret; } } } #[allow(dead_code)] fn get() -> T { get_word().parse().ok().unwrap() } fn main() { let n: usize = get(); const MOD: i64 = 1_000_000_007; let mut dp = vec![0; n + 1]; dp[0] = 1; for i in 3..n + 1 { for j in 0..n + 1 - i { dp[i + j] = (dp[i + j] + dp[j]) % MOD; } } println!("{}", dp[n]); }