use std::io::Write; use std::collections::*; type Map = BTreeMap; type Set = BTreeSet; type Deque = VecDeque; fn main() { input! { n: usize, p: [(i32, i32); n], } let mut p = p; p.sort(); let mut dp = vec![std::i32::MAX; n + 2]; dp[0] = 0; for (a, b) in p { let x = dp.upper_bound(&a); dp[x] = dp[x].min(b); } let ans = n - dp.iter().position(|p| *p == std::i32::MAX).unwrap() + 1; println!("{}", ans); } // ---------- 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 super slice ---------- pub trait SuperSlice { type Item; fn lower_bound(&self, key: &Self::Item) -> usize where Self::Item: Ord; fn lower_bound_by(&self, f: F) -> usize where F: FnMut(&Self::Item) -> std::cmp::Ordering; fn lower_bound_by_key(&self, key: &K, f: F) -> usize where K: Ord, F: FnMut(&Self::Item) -> K; fn upper_bound(&self, key: &Self::Item) -> usize where Self::Item: Ord; fn upper_bound_by(&self, f: F) -> usize where F: FnMut(&Self::Item) -> std::cmp::Ordering; fn upper_bound_by_key(&self, key: &K, f: F) -> usize where K: Ord, F: FnMut(&Self::Item) -> K; fn next_permutation(&mut self) -> bool where Self::Item: Ord; fn next_permutation_by(&mut self, f: F) -> bool where F: FnMut(&Self::Item, &Self::Item) -> std::cmp::Ordering; fn prev_permutation(&mut self) -> bool where Self::Item: Ord; } impl SuperSlice for [T] { type Item = T; fn lower_bound(&self, key: &Self::Item) -> usize where T: Ord, { self.lower_bound_by(|p| p.cmp(key)) } fn lower_bound_by(&self, mut f: F) -> usize where F: FnMut(&Self::Item) -> std::cmp::Ordering, { self.binary_search_by(|p| f(p).then(std::cmp::Ordering::Greater)) .unwrap_err() } fn lower_bound_by_key(&self, key: &K, mut f: F) -> usize where K: Ord, F: FnMut(&Self::Item) -> K, { self.lower_bound_by(|p| f(p).cmp(key)) } fn upper_bound(&self, key: &Self::Item) -> usize where T: Ord, { self.upper_bound_by(|p| p.cmp(key)) } fn upper_bound_by(&self, mut f: F) -> usize where F: FnMut(&Self::Item) -> std::cmp::Ordering, { self.binary_search_by(|p| f(p).then(std::cmp::Ordering::Less)) .unwrap_err() } fn upper_bound_by_key(&self, key: &K, mut f: F) -> usize where K: Ord, F: FnMut(&Self::Item) -> K, { self.upper_bound_by(|p| f(p).cmp(key)) } fn next_permutation(&mut self) -> bool where T: Ord, { self.next_permutation_by(|a, b| a.cmp(b)) } fn next_permutation_by(&mut self, mut f: F) -> bool where F: FnMut(&Self::Item, &Self::Item) -> std::cmp::Ordering, { use std::cmp::Ordering::*; if let Some(x) = self.windows(2).rposition(|a| f(&a[0], &a[1]) == Less) { let y = self.iter().rposition(|b| f(&self[x], b) == Less).unwrap(); self.swap(x, y); self[(x + 1)..].reverse(); true } else { self.reverse(); false } } fn prev_permutation(&mut self) -> bool where T: Ord, { self.next_permutation_by(|a, b| a.cmp(b).reverse()) } } // ---------- end super slice ----------