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.util.*;
import java.io.*;
import java.math.*;
 
public class Main {
    public static void main(String[] args) throws IOException {
        PrintWriter out = new PrintWriter(System.out);
        //Scanner sc = new Scanner();
        Reader in = new Reader();
        Main solver = new Main();
        solver.solve(out, in);
        out.flush();
        out.close();
 
    }
 
    static long INF = (long)1e18;
    static int maxn = (int)1e6+5;
    static int mod  = (int)1e9+7;
    static int n,m,k,t,q,d,p,min=0;
    
    
    void solve(PrintWriter out, Reader in) throws IOException{
        n = in.nextInt();
        m = in.nextInt();
        
        long[][][] dp = new long[m][n+2][n+2];
        for (int i = 1; i <= n; i++) {
            for (int j = n; j >= i; j--) {
                dp[0][i][j] = 1;
            }
        }
        
        long a = 0, b = 0;
        for (int z = 1; z < m; z++) {
            dp[z][1][n] = 1;
            for (int i = 1; i <=n ; i++) {
                for (int j = n; j >=i ; j--) {
                    if (i == 1 && j == n) continue;
                    dp[z][i][j] = (dp[z][i-1][j] + dp[z][i][j+1] - dp[z][i-1][j+1] + dp[z-1][i][j] + mod)%mod;
                }
            }
        }
        
        long ans = 0;
        for (int i = 1; i <= n; i++) {
            for (int j = n; j >= i; j--) {
                ans = (ans+dp[m-1][i][j])%mod;
            }
        }
        
        out.println(ans);
    }
    
    
    static class Reader {
 
    private InputStream mIs;
    private byte[] buf = new byte[1024];
    private int curChar;
    private int numChars;
 
    public Reader() {
        this(System.in);
    }
 
    public Reader(InputStream is) {
        mIs = is;
    }
 
    public int read() {
        if (numChars == -1) {
            throw new InputMismatchException();
 
    }
        if (curChar >= numChars) {
            curChar = 0;
            try {
                numChars = mIs.read(buf);
            } catch (IOException e) {
                throw new InputMismatchException();
            }
            if (numChars <= 0) {
                return -1;
            }
        }
        return buf[curChar++];
    }
 
    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 String next() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        StringBuilder res = new StringBuilder();
        do {
            res.appendCodePoint(c);
            c = read();
        } while (!isSpaceChar(c));
        return res.toString();
    }
 
    double nextDouble()
    {
        return Double.parseDouble(next());
    }
 
    public long nextLong() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        int sgn = 1;
        if (c == '-') {
            sgn = -1;
            c = read();
        }
        long res = 0;
        do {
            if (c < '0' || c > '9') {
                throw new InputMismatchException();
            }
            res *= 10;
            res += c - '0';
            c = read();
        } while (!isSpaceChar(c));
        return res * sgn;
    }
 
    public int nextInt() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        int sgn = 1;
        if (c == '-') {
            sgn = -1;
            c = read();
        }
        int res = 0;
        do {
            if (c < '0' || c > '9') {
                throw new InputMismatchException();
            }
            res *= 10;
            res += c - '0';
            c = read();
        } while (!isSpaceChar(c));
        return res * sgn;
    }
 
    public boolean isSpaceChar(int c) {
        return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
    }
 
    public boolean isEndOfLine(int c) {
        return c == '\n' || c == '\r' || c == -1;
    }
 
    }
}