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.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.InputStream;

import java.util.*;

public class Main {

    // global
    static int mod = 1_000_000_007;
    static long fact[];
    static long inverse[];

    static long pow(long a,int n) {
        long res=1;
        while (n>0) {
            if ((n-n/2*2)==1) {
                res=res*a%mod;
            }
            a=a*a%mod;
            n>>=1;
        }
        return res;
    }

    static long modinv(long n) {
        return pow(n, mod-2);
    }

    static long comb(int n,int k){
        if(n<0 || k<0 || n<k)return 0;
        return fact[n]*(inverse[k]*inverse[n-k]%mod) %mod;
    }

	public static void main(String[] args) {

        // main method
        fact=new long[200000];
        fact[0]=1;
        inverse=new long[200000];
        inverse[0]=1;
        for(int i=1;i<200000;i++){
            fact[i]=(fact[i-1]*(long)i)%mod;
            inverse[i]=modinv(fact[i]);
        }

		InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);

        int n = in.nextInt();
        int m = in.nextInt();

        long ans = 0L;
        for (int i=1;i<=n;i++) {
            long tmp = 0L;
            for (int j=0;j<=n-i;j++) {
                tmp = (tmp + comb(j+m-1, m-1))%mod;
            }
            ans = (ans+comb(i-1+m-1, m-1)*tmp%mod)%mod;
            // ans = (ans+comb(i-1+m-1, m-1)*comb(n-i+m-1, m-1)%mod)%mod;
            // ans = (ans+comb(i-1+m-1, m-1)*comb(i-1+m-1, m-1)%mod)%mod;
        }
        out.println(ans);

		out.close();
	}

	static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        }

        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

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

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

    }
}
