#include <bits/stdc++.h>
using namespace std;

template <long long mod>
class Mod
{
    long long value;
    void set_value(const long long x)
    {
        this->value = x % mod;
    }

public:
    Mod()
    {
        set_value(0ll);
    }

    template <typename T>
    Mod(T x = 0)
    {
        set_value((long long)x);
    }

    friend istream &operator>>(istream &is, Mod &x)
    {
        long long tmp;
        is >> tmp;
        x.set_value(tmp);
        return is;
    }

    friend ostream &operator<<(ostream &os, const Mod &x)
    {
        os << x.value;
        return os;
    }

    operator long long() const
    {
        return this->value;
    }

    template <typename T>
    bool operator<(const T x)
    {
        return this->value < (long long)x;
    }

    template <typename T>
    bool operator<=(const T x)
    {
        return this->value <= (long long)x;
    }

    template <typename T>
    bool operator>(const T x)
    {
        return this->value > (long long)x;
    }

    template <typename T>
    bool operator>=(const T x)
    {
        return this->value >= (long long)x;
    }

    template <typename T>
    bool operator==(const T x)
    {
        return this->value == (long long)x;
    }

    template <typename T>
    Mod &operator=(const T x)
    {
        set_value((long long)x);
        return *this;
    }

    template <typename T>
    Mod &operator&=(const T x)
    {
        set_value(this->value & (long long)x);
        return *this;
    }

    template <typename T>
    Mod &operator|=(const T x)
    {
        set_value(this->value | (long long)x);
        return *this;
    }

    template <typename T>
    Mod &operator^=(const T x)
    {
        set_value(this->value ^ (long long)x);
        return *this;
    }

    template <typename T>
    Mod &operator<<=(const T x)
    {
        set_value(this->value << (long long)x);
        return *this;
    }

    template <typename T>
    Mod &operator>>=(const T x)
    {
        set_value(this->value >> (long long)x);
        return *this;
    }

    template <typename T>
    Mod &operator+=(const T x)
    {
        set_value(this->value + (long long)x);
        return *this;
    }

    template <typename T>
    Mod &operator-=(const T x)
    {
        set_value(this->value - (long long)x + mod);
        return *this;
    }

    template <typename T>
    Mod &operator*=(const T x)
    {
        set_value(this->value * (long long)x);
        return *this;
    }

    template <typename T>
    Mod &operator/=(const T x)
    {
        long long a = (long long)x;
        long long b = mod;
        long long u = 1;
        long long v = 0;
        while (b)
        {
            long long t = a / b;
            a -= t * b;
            swap(a, b);
            u -= t * v;
            swap(u, v);
        }
        u %= mod;
        if (u < 0)
            u += mod;
        *this *= Mod(u);
        return *this;
    }

    template <typename T>
    Mod operator&(const T x) const
    {
        return Mod(*this) &= x;
    }

    template <typename T>
    Mod operator|(const T x) const
    {
        return Mod(*this) |= x;
    }

    template <typename T>
    Mod operator^(const T x) const
    {
        return Mod(*this) ^= x;
    }

    template <typename T>
    Mod operator<<(const T x) const
    {
        return Mod(*this) <<= x;
    }

    template <typename T>
    Mod operator>>(const T x) const
    {
        return Mod(*this) >>= x;
    }

    template <typename T>
    Mod operator+(const T x) const
    {
        return Mod(*this) += x;
    }

    template <typename T>
    Mod operator-(const T x) const
    {
        return Mod(*this) -= x;
    }

    template <typename T>
    Mod operator*(const T x) const
    {
        return Mod(*this) *= x;
    }

    template <typename T>
    Mod operator/(const T x) const
    {
        return Mod(*this) /= x;
    }

    Mod &operator++()
    {
        *this += 1;
        return *this;
    }

    Mod &operator--()
    {
        this->set_value(--this->value);
        return *this;
    }

    Mod operator++(auto)
    {
        Mod ret(*this);
        ++*this;
        return ret;
    }

    Mod operator--(auto)
    {
        Mod ret(*this);
        --*this;
        return ret;
    }
};

template <typename T, typename U>
T calc_combination(T x, U y)
{
    if (x < y)
    {
        return (T)0;
    }

    y = min(y, (U)x - y);
    T ans = 1;
    for (U i = 1; i <= y; i++)
    {
        ans *= x;
        ans /= i;
        x--;
    }
    return ans;
}

int main()
{
    const long long MOD = 1'000'000'007;
    long long X, Y;
    cin >> X >> Y;

    if ((X + Y) % 3 != 0)
    {
        cout << 0 << endl;
        return 0;
    }

    // a: (i + 1, j + 2)
    // b: (i + 2, j + 1)

    // a + b = (X + Y) / 3
    // a + 2b = X
    // 2a + b = Y
    long long a = Y - (X + Y) / 3;
    long long b = X - (X + Y) / 3;
    long long N = a + b;

    if (a < 0 || b < 0)
    {
        cout << 0 << endl;
        return 0;
    }

    cout << calc_combination(Mod<MOD>(a + b), a) << endl;
}


Measured memory_bytes: 256