Language: C++

#include <bits/stdc++.h>
#include<atcoder/all>
#define INF 1000000007
#define rep(i, N) for(ll i = 0; i < N; i++)
#define rep2(i, j, k) for(ll i = j; i < k; i++)
#define chmax(x, y) x = max(x, y)
#define chmin(x, y) x = min(x, y)
#define print(x) cout << x << "\n"
#define print2(x, y) cout << x << " " << y << "\n"
#define printv(vec) rep(lp, vec.size()) cout << vec[lp] << " "; print(""); 
#define show(x) cerr << #x << " = " << x << "\n";
#define ALL(v) v.begin(), v.end()
#define SUM(v) accumulate(ALL(v), 0)
#define MAX(v) *max_element(ALL(v))
#define MIN(v) *min_element(ALL(v))
#define SORT(v) sort(ALL(v))
#define REV(v) reverse(ALL(v))
#define pb(x) push_back(x)
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
typedef long long ll;
using namespace std;
using namespace atcoder;
using vl = vector<ll>;
using vvl = vector<vector<ll>>;
using vs = vector<string>;

const int mod = INF;
class mint {
public:
	ll x;
	mint(ll x = 0) : x((x % mod + mod) % mod) {}
	mint operator-() const { 
		return mint(-x);
	}
	mint& operator+=(const mint& a) {
		if ((x += a.x) >= mod) x -= mod;
		return *this;
	}
	mint& operator-=(const mint& a) {
		if ((x += mod - a.x) >= mod) x -= mod;
		return *this;
	}
	mint& operator*=(const  mint& a) {
		(x *= a.x) %= mod;
		return *this;
	}
	mint operator+(const mint& a) const {
		mint res(*this);
		return res += a;
	}
	mint operator-(const mint& a) const {
		mint res(*this);
		return res -= a;
	}
	mint operator*(const mint& a) const {
		mint res(*this);
		return res *= a;
	}
	mint pow(ll t) const {
		if (!t) return 1;
		mint a = pow(t >> 1);
		a *= a;
		if (t & 1) a *= *this;
		return a;
	}
	mint inv() const {
		return pow(mod - 2);
	}
	mint& operator/=(const mint& a) {
		return (*this) *= a.inv();
	}
	mint operator/(const mint& a) const {
		mint res(*this);
		return res /= a;
	}
	friend ostream& operator<<(ostream& os, const mint& m){
		os << m.x;
		return os;
	}
};

ll modpow(ll x, ll n, ll p = INF) {
	if (n == 0) return 1 % p;
	if (n % 2 == 0) return modpow(x * x % p, n / 2, p);
	else return x * modpow(x, n - 1, p) % p;
}

struct union_find{

	vl parent;
	vl sizes;

	void init(ll n) {
		rep(i, n) parent.push_back(i);
		rep(i, n) sizes.push_back(1);
	}

	ll root(ll n){
		if(parent[n] == n) return n;
		return parent[n] = root(parent[n]);
	}

	ll size(ll n) {
		return sizes[root(n)];
	}

	bool is_same(ll a, ll b){
		return root(a) == root(b);
	}

	void unite(ll a, ll b){
		if(is_same(a, b)) return;
		sizes[root(a)] += size(b);
		parent[root(b)] = root(a);
	}
	
	ll group_count(){
		ll ret = 0;
		rep(i, parent.size()) ret += (parent[i] == i);
		return ret;
	}
};

ll op(ll a, ll b) {
    return max(a, b);
}

ll e() {
    return -1;
}

void Main(){

	ll N, K;
	cin >> N >> K;
	vl v(N);
	rep(i, N) cin >> v[i];
    rep(i, N) v[i] += 3;
	
	segtree<ll, op, e> seg(N + 10);
 	vl dp(N + 10);
    dp[N - 1] = 1;
    seg.set(v[N - 1], dp[N - 1]);
    for(ll i = N - 2; i >= 0; i--){
      ll ma = seg.prod(v[i] - 4, v[i] + 4);
      dp[i] = ma + 1;
      ll tmp = seg.prod(v[i], v[i]);
      seg.set(v[i], max(tmp, dp[i]));
      //print2(i, dp[i]);
      //print(ma);
      //print("===");
    }
  
  ll ans = MAX(dp);
  print(ans);
	
}

int main(){
	
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	ll t = 1;
	//cin >> t;
	rep(i, t) Main();
	return 0;
	
}





Compiler output:
a.cc:2:9: fatal error: atcoder/all: No such file or directory
    2 | #include<atcoder/all>
      |         ^~~~~~~~~~~~~
compilation terminated.