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.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.StringTokenizer;

public class EducationalRound80C {

	public static void solve() {
		int n=s.nextInt();
		int m=s.nextInt();
		
		long[][] curr = new long[n][n];
		for(int i=0;i<n;i++) {
			Arrays.fill(curr[i], 1);
		}
		for(int i=1;i<m;i++) {
			Sum_Row(curr);
			Sum_Col(curr);
		}
		long ans = 0;
		for(int i=0;i<n;i++) {
			for(int j=0;j<n;j++) {
				if(j>=i) {
					ans += curr[i][j];
					ans%=mod;
				}
			}
		}
		out.println(ans);
	}
	public static long mod = (long)1e9+7;
	
	public static void Sum_Row(long[][] curr) {
		int n=curr.length;
		for(int i=0;i<n;i++) {
			for(int j=n-2;j>=0;j--) {
				curr[i][j]+=curr[i][j+1];
				curr[i][j]%=mod;
			}
		}
	}
	
	public static void Sum_Col(long[][] curr) {
		int n = curr.length;
		for(int j=0;j<n;j++) {
			for(int i=1;i<n;i++) {
				curr[i][j]+=curr[i-1][j];
				curr[i][j]%=mod;
			}
		}
	}

	public static void main(String[] args) {
		out = new PrintWriter(new BufferedOutputStream(System.out));
		s = new FastReader();
		solve();
		out.close();
	}

	public static FastReader s;
	public static PrintWriter out;

	public static class FastReader {
		BufferedReader br;
		StringTokenizer st;

		public FastReader() {
			br = new BufferedReader(new InputStreamReader(System.in));
		}

		String next() {
			while (st == null || !st.hasMoreTokens()) {
				try {
					st = new StringTokenizer(br.readLine());
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
			return st.nextToken();
		}

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

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

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

		String nextLine() {
			String str = "";
			try {
				str = br.readLine();
			} catch (Exception e) {
				e.printStackTrace();
			}
			return str;
		}
	}

	
}
