#include <iostream>
using namespace std;
using ll = long long;
template <ll M>
struct modular {
ll val;
// n >= 0
modular(const ll n) {
if (n < M)
val = n;
else if (n < 2 * M)
val = n - M;
else
val = n % M;
}
[[nodiscard]] modular operator +(const modular& rhs) const {
return val + rhs.val;
}
[[nodiscard]] modular operator -(const modular& rhs) const {
return val + M - rhs.val;
}
[[nodiscard]] modular operator *(const modular& rhs) const {
return val * rhs.val;
}
// p >= 0
[[nodiscard]] modular pow(const ll& p) const {
if (p == 0)
return 1;
if (p % 2 == 0)
return (*this * *this).pow(p / 2);
else
return *this * pow(p - 1);
}
[[nodiscard]] modular inv() const {
return pow(M - 2);
}
[[nodiscard]] modular operator /(const modular& rhs) const {
return *this * rhs.inv();
}
modular& operator +=(const modular& rhs) {
return *this = *this + rhs;
}
modular& operator -=(const modular& rhs) {
return *this = *this - rhs;
}
modular& operator *=(const modular& rhs) {
return *this = *this * rhs;
}
modular& operator /=(const modular& rhs) {
return *this = *this / rhs;
}
explicit operator ll() const {
return val;
}
};
template <ll M>
ostream& operator<<(ostream& os, const modular<M>& modular) {
cout << modular.val;
return os;
}
using mod = modular<1'000'000'007>;
mod nck(ll const& n, ll const& k) {
mod ans = 1;
for (ll i = n - k + 1; i <= n; i++)
ans *= i;
for (ll i = 2; i <= k; i++)
ans /= i;
return ans;
}
int main() {
ll b, c;
cin >> b >> c;
cout << nck(2 * c - b - 1, c - b) - nck(2 * c - b - 1, c - b - 1) << "\n";
}