#include <bits/stdc++.h>

#define REP(i, n) for (int i = 0; i < n; i++)
#define ALL(obj) obj.begin(), obj.end()

template <class T>
inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return 1;
    }
    return 0;
}
template <class T>
inline bool chmin(T& a, T b) {
    if (a > b) {
        a = b;
        return 1;
    }
    return 0;
}

const int iINF = 1e9;
const long long llINF = 1e18;
const int MOD = 1e9 + 7;

using namespace std;

const int MAX = 1000000;

vector<long long> fac(MAX + 1), inverseFac(MAX + 1);

long long modPow(long long x, long long n) {
    long long res = 1;
    while (n > 0) {
        if (n & 1) res = res * x % MOD;
        x = x * x % MOD;
        n >>= 1;
    }
    return res;
}

long long comb(long long a, long long b) {
    if (a == 0 && b == 0) return 1;
    if (a < b || a < 0) return 0;
    long long tmp = inverseFac[a - b] * inverseFac[b] % MOD;
    return tmp * fac[a] % MOD;
}

long long perm(long long a, long long b) {
    if (a < b) return 0;
    long long tmp = inverseFac[a - b] % MOD;
    return tmp * fac[a] % MOD;
}

long long dupc(long long a, long long b) {
    if (a == 0 && b == 0) return 1;
    if (a < 0 || b == 0) return 0;
    long long tmp = inverseFac[a - 1] * inverseFac[b] % MOD;
    return tmp * fac[a + b - 1] % MOD;
}

void init() {
    fac[0] = 1;
    inverseFac[0] = 1;
    for (long long i = 0; i < MAX; i++) {
        fac[i + 1] = fac[i] * (i + 1) % MOD;
        inverseFac[i + 1] = inverseFac[i] * modPow(i + 1, MOD - 2) % MOD;
    }
}

template <int MOD>
struct Fp {
    long long val;
    constexpr Fp(long long v = 0) noexcept : val(v % MOD) {
        if (val < 0) val += MOD;
    }
    constexpr int getmod() { return MOD; }
    constexpr Fp operator-() const noexcept { return val ? MOD - val : 0; }
    constexpr Fp operator+(const Fp& r) const noexcept {
        return Fp(*this) += r;
    }
    constexpr Fp operator-(const Fp& r) const noexcept {
        return Fp(*this) -= r;
    }
    constexpr Fp operator*(const Fp& r) const noexcept {
        return Fp(*this) *= r;
    }
    constexpr Fp operator/(const Fp& r) const noexcept {
        return Fp(*this) /= r;
    }
    constexpr Fp& operator+=(const Fp& r) noexcept {
        val += r.val;
        if (val >= MOD) val -= MOD;
        return *this;
    }
    constexpr Fp& operator-=(const Fp& r) noexcept {
        val -= r.val;
        if (val < 0) val += MOD;
        return *this;
    }
    constexpr Fp& operator*=(const Fp& r) noexcept {
        val = val * r.val % MOD;
        return *this;
    }
    constexpr Fp& operator/=(const Fp& r) noexcept {
        long long a = r.val, b = MOD, u = 1, v = 0;
        while (b) {
            long long t = a / b;
            a -= t * b;
            swap(a, b);
            u -= t * v;
            swap(u, v);
        }
        val = val * u % MOD;
        if (val < 0) val += MOD;
        return *this;
    }
    constexpr bool operator==(const Fp& r) const noexcept {
        return this->val == r.val;
    }
    constexpr bool operator!=(const Fp& r) const noexcept {
        return this->val != r.val;
    }
    friend constexpr ostream& operator<<(ostream& os,
                                         const Fp<MOD>& x) noexcept {
        return os << x.val;
    }

    friend constexpr Fp<MOD> modpow(const Fp<MOD>& a, long long n) noexcept {
        if (n == 0) return 1;
        auto t = modpow(a, n / 2);
        t = t * t;
        if (n & 1) t = t * a;
        return t;
    }
};

using mint = Fp<MOD>;

int main() {
    long long X, Y;
    cin >> X >> Y;
    if ((2 * X - Y) % 3 != 0) {
        cout << 0 << endl;
    } else {
        init();
        long long y = (2 * X - Y) / 3;
        long long x = X - 2 * y;

        if (x < 0 || y < 0) {
            cout << 0 << endl;
            return 0;
        }

        mint ans = comb(x + y, x);
        cout << ans << endl;
    }
    return 0;
}

Measured memory_bytes: 15872