//
//  main.cpp
//

#include <algorithm>
#include <array>
#include <assert.h>
#include <iomanip>
#include <iostream>
#include <limits>
#include <math.h>
#include <memory>
#include <memory>
#include <queue>
#include <random>
#include <set>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <vector>

using namespace std;

using ll = int64_t;
using ull = uint64_t;

template<typename T>
vector<T> make_vec_nd(T init, ll size) {
    return vector<T>(size, init);
}
template<typename T, typename... Args>
auto make_vec_nd(T init, ll size, Args... rest) {
    auto inner = make_vec_nd(init, rest...);
    return vector<decltype(inner)>(size, inner);
}

#define rep(i,a,b) for(ll i=(a);i<(b);i++)
#define rrep(i,a,b) for(ll i=(a)-1;i>=(b);i--)

namespace Util {
    template<typename INT>
    INT gcd_with_coef(INT x, INT y, INT* outCX, INT* outCY) {
        if (x < 0) {
            INT d = gcd_with_coef(-x, y, outCX, outCY);
            *outCX *= -1;
            return d;
        }
        if (y < 0) {
            INT d = gcd_with_coef(x, -y, outCX, outCY);
            *outCY *= -1;
            return d;
        }
        if (x > y) {
            return gcd_with_coef(y, x, outCY, outCX);
        }
        if (x == 0) {
            if (outCX != nullptr && outCY != nullptr) {
                *outCX = 0;
                *outCY = 1;
            }
            return y;
        }
        INT q = y / x;
        INT r = y % x;
        INT d = gcd_with_coef(r, x, outCY, outCX);
        if (outCX != nullptr && outCY != nullptr) {
            *outCX -= q * *outCY;
        }
        return d;
    }
}

struct Mod {
    static ll BASE;
    ll value = 0;
    static ll residue(ll value) { return (value % BASE + BASE) % BASE; }
    Mod(ll value)
    : value(residue(value)) {}
    Mod operator+(const Mod& rhs) const { return Mod(value + rhs.value); }
    void operator+=(const Mod& rhs) { *this = *this + rhs; }
    Mod operator-(const Mod& rhs) const { return Mod(value - rhs.value); }
    void operator-=(const Mod& rhs) { *this = *this - rhs; }
    Mod operator*(const Mod& rhs) const { return Mod(value * rhs.value); }
    void operator*=(const Mod& rhs) { *this = *this * rhs; }
    Mod operator/(const Mod& rhs) const { return *this * rhs.inv(); }
    void operator/=(const Mod& rhs) { *this = *this / rhs; }
    Mod inv() const {
        if (value == 0) {
            assert(false);
            throw "[Mod::inv] div by zero";
        }
        ll ans, sub;
        ll d = Util::gcd_with_coef<ll>(value, BASE, &ans, &sub);
        if (d != 1) {
            assert(false);
            throw "[Mod::inv] not invertible";
        }
        return ans;
    }
};
ll Mod::BASE = 1000000007;

int main() {
    ll X, Y;
    cin >> X >> Y;
    if ((X + Y) % 3 != 0) {
        cout << 0 << endl;
        return 0;
    }
    ll n_plus_m = (X + Y) / 3;
    ll N = X - n_plus_m;
    ll M = Y - n_plus_m;
    if (N < 0 || M < 0) {
        cout << 0 << endl;
        return 0;
    }
    // binom(N+M, N);
    vector<Mod> fact(N+M+1, (Mod)1);
    rep(n,1,N+M+1) {
        fact[n] = fact[n-1] * (Mod)n;
    }
    Mod ans = fact[N+M] / (fact[N] * fact[M]);
    cout << ans.value << endl;
}



Measured memory_bytes: 5632