#include <bits/stdc++.h>
using namespace std;
#define int long long
const int INF = 1e9 + 7;
const int N = 2e5+1;

int fakt[N], inv[N];

int po(int a, int b)
{
    int res = 1;
    while(b)
    {
        if(b & 1) res = res * a % INF;
        a = a * a % INF;
        b >>= 1;
    }
    return res;
}

int alatt(int a, int b)
{
    if(a < b) return 0;
    return (fakt[a] * inv[b] % INF * inv[a-b] % INF);
}

signed main() {
    ios::sync_with_stdio(false);cin.tie(nullptr);
    fakt[0] = inv[0] = 1;
    for(int i = 1; i < N; i++)
    {
        fakt[i] = i * fakt[i-1] % INF;
        inv[i] = po(fakt[i], INF-2);
    }
	int b, c; cin >> b >> c;
    int all = alatt(2*c - b - 1, c - b);
    int rossz = alatt(2*c - b - 1, c - b - 1);
    cout << (all - rossz + INF) % INF;
}