//https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8 より 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_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_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") }; } // fn calc(a: &mut [usize]) -> usize { if a.len() <= 1 { return 0; } let m = a.len() / 2; let mut ans = calc(&mut a[..m]) + calc(&mut a[m..]); let mut buf = vec![]; let mut i = 0; let mut j = m; while i < m && j < a.len() { if a[i] <= a[j] { buf.push(a[i]); i += 1; } else { ans += m - i; buf.push(a[j]); j += 1; } } while i < m { buf.push(a[i]); i += 1; } for (a, b) in a.iter_mut().zip(buf.iter()) { *a = *b; } ans } fn run() { input! { n: usize, a: [usize1; n], b: [usize1; n], } let mut x = vec![0; n]; for (i, b) in b.iter().enumerate() { x[*b] = i; } let mut a = a; for a in a.iter_mut() { *a = x[*a]; } let ans = calc(&mut a); println!("{}", ans); } fn main() { run(); }