#include <iostream>
#include <cstdio>
#define ll long long
const int N=200005;//1e5越界
const ll M=1e9+7;
using namespace std;
ll fac[N]={1,1},inv[N]={1,1},fi[N]={1,1};//fac[i]是i的階乘，inv[i]是i的逆元,fi[i]是i之前的很多逆元求得階乘，（將除i取模變為乘i的逆元取模

void init()
{
    for(int i=2;i<N;i++)
    {
        fac[i]=fac[i-1]*i%M;
        inv[i]=(M-M/i)*inv[M%i]%M;
        fi[i]=inv[i]*fi[i-1]%M;
    }//遞推儲存fac階乘，和fi各個逆元取模相乘
}
ll C(ll a,ll b)
{
    return fac[a]*fi[b]%M*fi[a-b]%M;//C(a,b)=a!/(b!*(a-b)!)
}
int main()
{
    init();
    int n,m;
    while(~scanf("%d%d",&n,&m))
    {
        cout<<C(m+n-4,m-2)<<endl;//求組合數
    }
    return 0;
}