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.util.*;
import java.text.*;
import java.lang.*;
import java.math.*;
 
public class Main{
    static ArrayList[] a = new ArrayList[200001];
    
    public void solve () throws IOException  {
       
    	InputReader in = new InputReader(System.in);
        PrintWriter pw = new PrintWriter(System.out);
        int n = in.nextInt();
        int m = in.nextInt();
        long dp[][] = new long [m][n + 1];
        long dp1[][] = new long [m][n + 1];
    	long pre[] = new long[n + 1];
    	Arrays.fill(pre, 1L);
    	pre[0] = 0L;
        for(int i = 0 ; i < m ; i++) {
        	for(int j = 1 ; j <= n ; j++) {
        		dp[i][j] = pre[j];
        	}
        	
        	for(int j = 1 ; j <= n ; j++) {
        		pre[j] = (pre[j - 1] + dp[i][j]);
        		pre[j] %= mod;
        	}
        }
        long suf[] = new long [n + 5];
        Arrays.fill(suf, 1L);
        suf[n + 1] = 0L;
        for(int i = 0 ; i < m ; i++) {
        	for(int j = n ; j > 0 ; j--) {
        		dp1[i][j] = suf[j];
        	}
        	
        	for(int j = n ; j > 0 ; j--) {
        		suf[j] = (suf[j + 1] + dp1[i][j]);
        		suf[j] %= mod;
        	}
        }
      
        long ans = 0L;
        for(int i = 1 ; i <= n ; i++) {
        	for(int j = i ; j <= n ; j++) {
        		ans += (dp[m - 1][i] * dp1[m - 1][j])%mod;
        		ans %= mod;
        	}
        }
        pw.println(ans);
        pw.flush();
        pw.close();
    }
    public static void main(String[] args) throws Exception {
        
        
        new Thread(null,new Runnable() {
            public void run() {
                    try {
                        new Main().solve();
                    } catch (FileNotFoundException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    } catch (IOException e) {
						// TODO Auto-generated catch block
						e.printStackTrace();
					}
            }
        },"1",1<<26).start();
        
        
    }
   
    static void debug(Object... o) {
        System.out.println(Arrays.deepToString(o));
        }
        
        static class InputReader 
        {
        private final InputStream stream;
        private final byte[] buf = new byte[8192];
        private int curChar, snumChars;
        private SpaceCharFilter filter;
 
        public InputReader(InputStream stream) 
        {
            this.stream = stream;
        }
        public int snext() 
        {
            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 = snext();
            while (isSpaceChar(c)) 
            {
                c = snext();
            }
            int sgn = 1;
            if (c == '-')
            {
                sgn = -1;
                c = snext();
            }
            int res = 0;
            do 
            {
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = snext();
            } while (!isSpaceChar(c));
            return res * sgn;
        }
 
        public long nextLong()
        {
            int c = snext();
            while (isSpaceChar(c)) 
            {
                c = snext();
            }
            int sgn = 1;
            if (c == '-') 
            {
                sgn = -1;
                c = snext();
            }
            long res = 0;
            do 
            {
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = snext();
            } while (!isSpaceChar(c));
            return res * sgn;
        }
 
        public int[] nextIntArray(int n) 
        {
            int a[] = new int[n];
            for (int i = 0; i < n; i++) 
            {
                a[i] = nextInt();
            }
            return a;
        }
 
        public String readString()
        {
            int c = snext();
            while (isSpaceChar(c)) 
            {
                c = snext();
            }
            StringBuilder res = new StringBuilder();
            do 
            {
                res.appendCodePoint(c);
                c = snext();
            } while (!isSpaceChar(c));
            return res.toString();
        }
 
        public String nextLine() 
        {
            int c = snext();
            while (isSpaceChar(c))
                c = snext();
            StringBuilder res = new StringBuilder();
            do 
            {
                res.appendCodePoint(c);
                c = snext();
            } while (!isEndOfLine(c));
            return res.toString();
        }
 
        public boolean isSpaceChar(int c) 
        {
            if (filter != null)
                return filter.isSpaceChar(c);
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }
 
        private boolean isEndOfLine(int c) 
        {
            return c == '\n' || c == '\r' || c == -1;
        }
 
        public interface SpaceCharFilter
        {
            public boolean isSpaceChar(int ch);
        }
    }
        public static long mod = 1000000007;
        public static int d;
        public static int p;
        public static int q;
        public void extended(int a,int b) {
            if(b==0) {
                d=a;
                p=1;
                q=0;
            }
            else
            {
                extended(b,a%b);
                int temp=p;
                p=q;
                q=temp-(a/b)*q;
            }
        }
       
        
        public static long binaryExponentiation(long x,long n)
        {
            long result=1;
            while(n>0)
            {
                if(n % 2 ==1)
                    result=result * x;
                x=x*x;
                n=n/2;
            }
            return result;
        }
        
        public static long[] shuffle(long[] a,Random gen)
        {
            int n = a.length;
            for(int i=0;i<n;i++)
            {
                int ind = gen.nextInt(n-i)+i;
                long temp = a[ind];
                a[ind] = a[i];
                a[i] = temp;
            }
            return a;
        }
        
        public static void swap(int a, int b){
            int temp = a;
            a = b;
            b = temp;
        }
        
        public static HashSet<Integer> primeFactorization(int n)
        {
            HashSet<Integer> a =new HashSet<Integer>();
            for(int i=2;i*i<=n;i++)
            {
                while(n%i==0)
                {
                    a.add(i);
                    n/=i;
                }
            }
            if(n!=1)
                a.add(n);
            return a;
        }
        
        public static void sieve(boolean[] isPrime,int n)
        {
            for(int i=1;i<n;i++)
                isPrime[i] = true;
            
            isPrime[0] = false;
            isPrime[1] = false;
            
            for(int i=2;i*i<n;i++)
            {
                if(isPrime[i] == true)
                {
                    for(int j=(2*i);j<n;j+=i)
                        isPrime[j] = false;
                }
            }
        }
        
        public static long GCD(long n,long m)
        {
            if(m==0)
                return n;
            else
                return GCD(m,n%m);
        }
        public static long LCM (long a,long b) {
            return ((a*b)/(GCD(a,b)));
        }
        
        static class pair implements Comparable<pair>
        {
            Integer y , x ;
            
            pair(int l,Integer y)
            {
                this.x=l;
                this.y=y;
            }

           
            public int compareTo(pair o) {
                int result = x.compareTo(o.x);
                if(result==0)
                    result = y.compareTo(o.y);
                
                return result;
            }  
            
            public String toString()
            {
                return x+" "+y;
            }
            
            public boolean equals(Object o)
            {
                if (o instanceof pair)
                {
                    pair p = (pair)o;
                    return p.x == x && p.y == y ;
                }
                return false;
            }
            public int hashCode()
            {
                return new Long(x).hashCode()*3 + new Long(y).hashCode();
                
            }
        }
        public static int binaryExponentiation(int x,int n)
        {
            int result=1;
            while(n>0)
            {
                if(n % 2 ==1)
                    result=result * x;
                x=x*x;
                n=n/2;
            }
            return result;
        }
        
       
        
        public static int modularExponentiation(int x,int n,int M)
        {
            int result=1;
            while(n>0)
            {
                if(n % 2 ==1)
                    result=(result * x)%M;
                x=(x%M*x)%M;
                n=n/2;
            }
            return result;
        }
        
        public static long modularExponentiation(long x,long n,long M)
        {
            long result=1;
            while(n>0)
            {
                if(n % 2 ==1)
                    result=(result%M * x%M)%M;
                x=(x%M * x%M)%M;
                n=n/2;
            }
            return result;
        }
        
        public static long modInverse(int A,int M)
        {
            return modularExponentiation(A,M-2,M);
        }
        
        public static long modInverse(long A,long M)
        {
            return modularExponentiation(A,M-2,M);
        }
        static class Segment{ 
    		int seg[]; 
    		int a[];
    		int lazy[];
    	    Segment (int n,int b[]){
    			seg=new int[4*n];
    			lazy=new int[4*n];
    			a=new int[b.length];
    			a=b.clone();
    		}
    	    public void build(int node,int start,int end) {
    	    	if(start==end) {
    	    		seg[node]=a[start];
    	    		return ;
    	    	}
    	    	int mid=(start+end)/2;
    	    	build(2*node+1,start,mid);
    	    	build(2*node+2,mid+1,end);
    	    	seg[node]=seg[2*node+1]+seg[2*node+2];
    	    }
    	    public void update(int node,int start,int end,int id,int val) {
    	    	if(start==end) {
    	    		seg[node]=a[start]=val;
    	    		return;
    	    	}
    	    	int mid=(start+end)/2;
    	    	if(id>=start && id<=mid) {
    	    		update(2*node+1,start,mid,id,val);
    	    	}
    	    	else
    	    		update(2*node+2,mid+1,end,id,val);
    	    	seg[node]=seg[2*node+1]+seg[2*node+2];
    	    }
    	    public int query(int node,int start,int end,int l,int r) {
    	    	if(l>end || r<start)
    	    		return 0;
    	    	if(start>=l && end<=r)
    	    		return seg[node];
    	    	
    	    	int  mid=(start+end)/2;
    	    	return (query(2*node+1,start,mid,l,r)+query(2*node+2,mid+1,end,l,r));
    	    }
    	    public void updateRange(int node,int start,int end,int l,int r,int val) {
    	    	if(lazy[node]!=0) {
	    			seg[node] += lazy[node];
    	    		if(start!=end) {
    	    			lazy[2*node+1]+=lazy[node];
    	    			lazy[2*node+2]+=lazy[node];
    	    		}
    	    		lazy[node]=0;
    	    	}
    	    	if(l>end || r<start)
    	    		return ;
    	    	if(start>=l && end<=r) {
    	    		seg[node] += val;
    	    		if(start!=end) {
    	    			lazy[2*node+1]+=val;
    	    			lazy[2*node+2]+=val;
    	    		}
    	    		lazy[node]=0;
    	    		return ;
    	    	}
    	    	int mid=(start+end)/2;
    	    	updateRange(2*node+1,start,mid,l,r,val);
    	    	updateRange(2*node+2,mid+1,end,l,r,val);
    	    	seg[node]=seg[2*node+1]+seg[2*node+2];
    	    }
    	    public int queryRange(int node,int start,int end,int l,int r) {
    	    	if(l>end || r<start)
    	    		return 0;
    	    	if(lazy[node]!=0) {
    	    		seg[node] += lazy[node];
    	    		if(start!=end) {
    	    			lazy[2*node+1]+=lazy[node];
    	    			lazy[2*node+2]+=lazy[node];
    	    		}
    	    		lazy[node]=0;
    	    	}
    	    	if(start>=l && end<=r)
    	    		return seg[node];
    	    	
    	    	int  mid=(start+end)/2;
    	    	return (queryRange(2*node+1,start,mid,l,r)+queryRange(2*node+2,mid+1,end,l,r));
    	    }
    	    
    	}
       
        
                    
         
}