dp(k, v)：k是等差数列的最后一个元素，v是以该元素结尾的等差数列数量

枚举每一个数查看dp(k - d(公差))是否存在，存在就加到res，
然后更新dp(k, v)为dp(k, v + res + 1)中

import java.util.*;
import java.io.*;

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String[] input = br.readLine().split(" ");
        int N = Integer.parseInt(input[0]);
        int k = Integer.parseInt(input[1]);

        String[] numsStr = br.readLine().split(" ");
        int[] l = new int[N];
        for (int i = 0; i < N; ++i) {
            l[i] = Integer.parseInt(numsStr[i]);
        }

        final int MOD = 1000000007;
        Map<Integer, Integer> dp = new HashMap<>();
        long ans = 0;

        for (int i : l) {
            int res = 0;
            if (dp.containsKey(i - k)) {
                res = dp.get(i - k);
            }
            ans = (ans + res) % MOD;
            dp.put(i, (dp.getOrDefault(i, 0) + res + 1) % MOD);
        }

        System.out.println(ans);
    }
}