Problem:
Score : 400 points

Problem Statement

You are given a sequence A_1, A_2, ..., A_N and an integer K.

Print the maximum possible length of a sequence B that satisfies the following conditions:

B is a (not necessarily continuous) subsequence of A.

For each pair of adjacents elements of B, the absolute difference of the elements is at most K.

Constraints

1 \leq N \leq 300,000

0 \leq A_i \leq 300,000

0 \leq K \leq 300,000

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N K
A_1
A_2
:
A_N

Output

Print the answer.

Sample Input 1

10 3
1
5
4
3
8
6
9
7
2
4

Sample Output 1

7

For example, B = (1, 4, 3, 6, 9, 7, 4) satisfies the conditions.

It is a subsequence of A = (1, 5, 4, 3, 8, 6, 9, 7, 2, 4).

All of the absolute differences between two adjacent elements (|1-4|, |4-3|, |3-6|, |6-9|, |9-7|, |7-4|) are at most K = 3.

Solution in C++ (GCC 9.2.1 with AC Library v1.1) (judge verdict: Wrong Answer)

#include<iostream>
#include<string>
#include<atcoder/dsu>
#include<algorithm>
#include<vector>
using namespace std;
using namespace atcoder;
using ll=long long;
int main(){

  int N,K;
  cin>>N>>K;
  vector<int>A(N);
  for(int i=0;i<=N-1;i++)cin>>A[i];
  vector<int>dp(N);
  dp[0]=1;
  for(int i=0;i<=N-1;i++){
  
    for(int j=0;j<=i-1;j++){
    
      if(abs(A[i]-A[j])<=3)dp[i]=max(dp[i],dp[j]+1);
    }
  }
  cout<<dp[N-1];
  return 0;
}