#include <bits/stdc++.h>
#define rep(i,l,r) for (int i = l; i < r; i++)
#define pb push_back
#define debug(x) cerr << #x << " : " << x << endl;
using namespace std;
typedef long long ll;
const ll N = 5e5+20,mod = 1e9+7;
int poww(int a,int k){
if (!k) return 1;
if (k == 1) return a;
int r = poww(a,k/2);
return 1ll*r*r%mod*poww(a,k&1)%mod;
}
ll fac[N],inv[N];
int main(){
ios :: sync_with_stdio(0); cin.tie(0); cout.tie(0);
fac[0] = 1;
inv[0] = 1;
int n,r;
cin >> n >> r;
rep(i,1,n+r){
fac[i] = fac[i-1]*i%mod;
inv[i] = poww(fac[i],mod-2);
}
cout << fac[r+n-1]*inv[n-1]%mod*inv[r]%mod;
}
