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.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.InputMismatchException;

public class P1288C {
	//author: Nagabhushan S Baddi

	private static int n, m;
	private static long[] a;
	private static long d;
	private static String s;
	private static HashMap<Integer, ArrayList<Integer>> g;
//	private static int MOD = (int)1e9+7;

	public static void main(String[] args) {
		n = ini();
		m = ini();

//		pd(solve(0, 1, n));
		
		long[][][] dp = new long[m+1][n+1][n+1];
		
		for(int i=0; i<n+1; i++) {
			for(int j=0; j<n+1; j++) {
				dp[m][i][j]=1;
			}
		}
		
		for(int i=m-1; i>=0; i--) {
			long[][] dp2 = new long[n+1][n+1];
			long[] dp3 = new long[n+1];
			for(int j=1; j<=n; j++) {
				for(int k=1; k<=j; k++) {
					dp3[j]=(dp3[j]+dp[i+1][j][k])%MOD;
				}
			}
			for(int p1=1; p1<=n; p1++) {
				for(int p2=1; p2<=n; p2++) {
					dp2[p1][p2] = (dp2[p1][p2]+(p2-1>=1?dp2[p1][p2-1]:0)+dp3[p2])%MOD;
				}
			}
			for(int p1=1; p1<=n; p1++) {
				for(int p2=1; p2<=n; p2++) {
					dp[i][p1][p2] = dp2[p1][p2];
				}
			}
		}
		
		println(dp[0][1][n]);
		
		out.flush();
		out.close();

	}
	
//	1, 2, 3, 4, 5
	
	
	
	
	private static long solve(int i, int p1, int p2) {
		if (i==m) return 1;
		
		long ans = 0;
		
		for(int j=p1; j<=n; j++) {
			for(int k=1; k<=p2; k++) {
				if (j<=k)
					ans += solve(i+1, j, k);
			}
		}
		return ans;
	}

	//CONSTANTS
	private static final int MOD = (int) 1e9 + 7;

	//NONPROBLEM CODE

	private static InputReader in = new InputReader(System.in);
	private static PrintWriter out = new PrintWriter(System.out);

	private static class InputReader {

		private final InputStream stream;
		private final byte[] buf = new byte[8192];
		private int curChar, snumChars;

		public InputReader(InputStream st) {
			this.stream = st;
		}

		public int read() {
			if (snumChars == -1)
				throw new InputMismatchException();
			if (curChar >= snumChars) {
				curChar = 0;
				try {
					snumChars = stream.read(buf);
				} catch (IOException e) {
					throw new InputMismatchException();
				}
				if (snumChars <= 0)
					return -1;
			}
			return buf[curChar++];
		}

		public int nextInt() {
			int c = read();
			while (isSpaceChar(c)) {
				c = read();
			}
			int sgn = 1;
			if (c == '-') {
				sgn = -1;
				c = read();
			}
			int res = 0;
			do {
				res *= 10;
				res += c - '0';
				c = read();
			} while (!isSpaceChar(c));
			return res * sgn;
		}

		public long nextLong() {
			int c = read();
			while (isSpaceChar(c)) {
				c = read();
			}
			int sgn = 1;
			if (c == '-') {
				sgn = -1;
				c = read();
			}
			long res = 0;
			do {
				res *= 10;
				res += c - '0';
				c = read();
			} while (!isSpaceChar(c));
			return res * sgn;
		}

		public String readString() {
			int c = read();
			while (isSpaceChar(c)) {
				c = read();
			}
			StringBuilder res = new StringBuilder();
			do {
				res.appendCodePoint(c);
				c = read();
			} while (!isSpaceChar(c));
			return res.toString();
		}

		public String nextLine() {
			int c = read();
			while (isSpaceChar(c))
				c = read();
			StringBuilder res = new StringBuilder();
			do {
				res.appendCodePoint(c);
				c = read();
			} while (!isEndOfLine(c));
			return res.toString();
		}

		public boolean isSpaceChar(int c) {
			return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
		}

		private boolean isEndOfLine(int c) {
			return c == '\n' || c == '\r' || c == -1;
		}

	}

	//SORT SHORTCUTS

	private static void sort(int[] a) {
		int n = a.length;
		Integer[] b = new Integer[n];
		for (int i = 0; i < n; i++) {
			b[i] = a[i];
		}

		Arrays.sort(b);

		for (int i = 0; i < n; i++) {
			a[i] = b[i];
		}
	}

	private static void sort(long[] a) {
		int n = a.length;
		long[] b = new long[n];
		for (int i = 0; i < n; i++) {
			b[i] = a[i];
		}

		Arrays.sort(b);

		for (int i = 0; i < n; i++) {
			a[i] = b[i];
		}
	}

	//INPUT SHORTCUTS

	private static int[] ina(int n) {
		int[] temp = new int[n];
		for (int i = 0; i < n; i++) {
			temp[i] = in.nextInt();
		}
		return temp;
	}

	private static int ini() {
		return in.nextInt();
	}

	private static long inl() {
		return in.nextLong();
	}

	private static String ins() {
		return in.readString();
	}

	//PRINT SHORTCUTS

	private static void println(Object... o) {
		for (Object x : o) {
			out.write(x + "");
		}
		out.write("\n");
	}

	private static void pd(Object... o) {
		for (Object x : o) {
			out.write(x + "");
		}
		out.flush();
		out.write("\n");
	}

	private static void print(Object... o) {
		for (Object x : o) {
			out.write(x + "");
		}
	}

	//GRAPH SHORTCUTS

	private static HashMap<Integer, ArrayList<Integer>> intree(int n) {

		HashMap<Integer, ArrayList<Integer>> g = new HashMap<>();
		for (int i = 0; i < n; i++) {
			g.put(i, new ArrayList<>());
		}

		for (int i = 0; i < n - 1; i++) {
			int u = ini() - 1;
			int v = ini() - 1;
			g.get(u).add(v);
			g.get(v).add(u);
		}

		return g;
	}

	private static HashMap<Integer, ArrayList<Integer>> ingraph(int n, int m) {
		HashMap<Integer, ArrayList<Integer>> g = new HashMap<>();

		for (int i = 0; i < n; i++) {
			g.put(i, new ArrayList<>());
		}

		for (int i = 0; i < m; i++) {
			int u = ini() - 1;
			int v = ini() - 1;
			g.get(u).add(v);
			g.get(v).add(u);
		}

		return g;

	}

	private static HashMap<Integer, ArrayList<Edge>> inweightedgraph(int n, int m) {
		HashMap<Integer, ArrayList<Edge>> g = new HashMap<>();

		for (int i = 0; i < n; i++) {
			g.put(i, new ArrayList<>());
		}

		for (int i = 0; i < m; i++) {
			int u = ini() - 1;
			int v = ini() - 1;
			int w = ini();
			Edge edge = new Edge(u, v, w);
			g.get(u).add(edge);
			g.get(v).add(edge);
		}

		return g;

	}

	private static class Edge implements Comparable<Edge> {
		private int u, v;
		private long w;

		public Edge(int a, int b, long c) {
			u = a;
			v = b;
			w = c;
		}

		public int other(int x) {
			return (x == u ? v : u);
		}

		public int compareTo(Edge edge) {
			return Long.compare(w, edge.w);
		}
	}

	private static class Pair {
		private int u, v;

		public Pair(int a, int b) {
			u = a;
			v = b;
		}

		public int hashCode() {
			return u + v + u * v;
		}

		public boolean equals(Object object) {
			Pair pair = (Pair) object;
			return u == pair.u && v == pair.v;
		}
	}

	private static class Node implements Comparable<Node> {
		private int u;
		private long dist;

		public Node(int a, long b) {
			u = a;
			dist = b;
		}

		public int compareTo(Node node) {
			return Long.compare(dist, node.dist);
		}
	}

	//MATHS AND NUMBER THEORY SHORTCUTS

	private static int gcd(int a, int b) {
		//O(log(min(a,b)))
		if (b == 0)
			return a;

		return gcd(b, a % b);
	}

	private static long modExp(long a, long b) {
		if (b == 0)
			return 1;

		a %= MOD;

		long exp = modExp(a, b / 2);

		if (b % 2 == 0) {
			return (exp * exp) % MOD;
		} else {
			return (a * ((exp * exp) % MOD)) % MOD;
		}
	}
}
