You are given two integers n and m. Calculate the number of pairs of arrays (a, b) such that:

  * the length of both arrays is equal to m; 
  * each element of each array is an integer between 1 and n (inclusive); 
  * a_i ≤ b_i for any index i from 1 to m; 
  * array a is sorted in non-descending order; 
  * array b is sorted in non-ascending order. 



As the result can be very large, you should print it modulo 10^9+7.

Input

The only line contains two integers n and m (1 ≤ n ≤ 1000, 1 ≤ m ≤ 10).

Output

Print one integer – the number of arrays a and b satisfying the conditions described above modulo 10^9+7.

Examples

Input


2 2


Output


5


Input


10 1


Output


55


Input


723 9


Output


157557417

Note

In the first test there are 5 suitable arrays: 

  * a = [1, 1], b = [2, 2]; 
  * a = [1, 2], b = [2, 2]; 
  * a = [2, 2], b = [2, 2]; 
  * a = [1, 1], b = [2, 1]; 
  * a = [1, 1], b = [1, 1]. 

import java.io.*;
import java.lang.reflect.Array;
import java.util.*;

import static java.lang.Math.*;

public class Main {
    long mod = (long) 1e9 + 7;

    void run() throws IOException {
        int n = nextInt();
        int m = nextInt();
        long[][] dp_a = new long[m + 1][n + 1];
        long[][] dp_b = new long[m + 1][n + 1];
        for (int i = 1; i < n + 1; i++) {
            dp_a[1][i] = 1;
        }
        for (int len = 2; len < m + 1; len++) {
            for (int last = 1; last < n + 1; last++) {
                for (int i = last; i > 0; i--) {
                    dp_a[len][last] += dp_a[len - 1][i];
                    dp_a[len][last] %= mod;
                }
            }
        }
        for (int i = 1; i < n + 1; i++) {
            dp_b[1][i] = 1;
        }
        for (int len = 2; len < m + 1; len++) {
            for (int firts = 1; firts < n + 1; firts++) {
                for (int i = firts; i < n + 1; i++) {
                    dp_b[len][firts] += dp_b[len - 1][i];
                    dp_b[len][firts] %= mod;
                }
            }
        }
        long ans = 0;
        for (int ends = 1; ends < n + 1; ends++) {
            long cnt = 0;
            for (int i = ends; i < n + 1; i++) {
                cnt += dp_b[m][i];
                cnt %= mod;
            }
            ans += dp_a[m][ends] * cnt;
            ans %= mod;
        }
        pw.print(ans);
        pw.close();
    }

    class point {
        int x, y;

        public point(int a, int b) {
            x = a;
            y = b;
        }
    }

    class pointComp implements Comparator<point> {

        @Override
        public int compare(point o1, point o2) {
            if (o1.x == o2.x) return Integer.compare(o1.y, o2.y);
            return Integer.compare(o1.x, o2.x);
        }
    }

    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    //BufferedReader br = new BufferedReader(new FileReader("pobeda.in"));

    StringTokenizer st = new StringTokenizer("");
    PrintWriter pw = new PrintWriter(System.out);
    //PrintWriter pw = new PrintWriter("pobeda.out");

    int nextInt() throws IOException {
        return Integer.parseInt(next());
    }

    String next() throws IOException {
        while (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }

    long nextLong() throws IOException {
        return Long.parseLong(next());
    }

    double nextDouble() throws IOException {
        return Double.parseDouble(next());
    }

    public Main() throws FileNotFoundException {
    }

    public static void main(String[] args) throws IOException {
        new Main().run();
    }
}