// UUID: ffd7be8c-c6a2-4d28-bdef-3854fe119e83
#include <bits/stdc++.h>
using namespace std;
#define int long long
#define MOD 1000000007

int fpow(int a, int b){
    int k = 1;
    for(int i = 0; (1<<i) <= b; i++){
        if((1<<i)&b){
            k= (k*a)%MOD;
        }
        a*= a;
        a%= MOD;
    }
    return k;
}
int t[1000000] = {1};

int n_c_k(int n, int k){
    return ((t[n]* fpow(t[k], MOD -2))%MOD * fpow(t[n-k], MOD -2))%MOD;
}

signed main() {
    int c,b;
    cin >> b >> c;
    for(int i = 1; i < 1000000; i++){
        t[i] = (t[i-1]* i)%MOD;    
    }
    c--;
    cout << (MOD+n_c_k(b+c, c)-n_c_k(b+c, c+1))%MOD;
}