#include <bits/stdc++.h>
#define lli long long int
#define MODV 1000000007
#define INF INT_MAX // 2147483647
#define INFLL LLONG_MAX // 9223372036854775807
#define rep(i, n) for(lli i=0, i##_len=(lli)(n); i<i##_len; i++)
#define repf(i, n) for(lli i=1, i##_len=(lli)(n+1); i<i##_len; i++)
#define per(i, n) for(lli i=((lli)(n))-1; i>=0; i--)
#define perf(i, n) for(lli i=((lli)(n)); i>0; i--)
#define all(v) v.begin(), v.end()
#define endl "\n"
#define vi vector<lli>
#define vvi vector<vector<lli>>
#define Yes() cout << "Yes" << endl
#define YES() cout << "YES" << endl
#define No() cout << "No" << endl
#define NO() cout << "NO" << endl
template<class T>bool chmax(T &a, const T &b){ if(a<b){ a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b){ if(b<a){ a=b; return 1; } return 0; }
using namespace std;

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;
    }
};

template<class T> struct BiCoef {
    vector<T> fact_, inv_, finv_;
    constexpr BiCoef() {}
    constexpr BiCoef(int n) noexcept : fact_(n, 1), inv_(n, 1), finv_(n, 1) { init(n); }
    constexpr void init(int n) noexcept { fact_.assign(n, 1), inv_.assign(n, 1), finv_.assign(n, 1);
        int MOD = fact_[0].getmod();
        for(int i = 2; i < n; i++){
            fact_[i] = fact_[i-1] * i;
            inv_[i] = -inv_[MOD%i] * (MOD/i);
            finv_[i] = finv_[i-1] * inv_[i];
        }
    }
    constexpr T com(int n, int k) const noexcept {
        if (n < k || n < 0 || k < 0) return 0;
        return fact_[n] * finv_[k] * finv_[n-k];
    }
    constexpr T fact(int n) const noexcept {
        if (n < 0) return 0;
        return fact_[n];
    }
    constexpr T inv(int n) const noexcept {
        if (n < 0) return 0;
        return inv_[n];
    }
    constexpr T finv(int n) const noexcept {
        if (n < 0) return 0;
        return finv_[n];
    }
};

const int MOD = MODV;
using mint = Fp<MOD>;

mint solve(lli x, lli y){
    if((x+y)%3 != 0) return 0;
    lli n = (-x + 2*y) / 3.0;
    lli m = (2*x - y) / 3.0;
    if(n<0 || m<0) return 0;
    BiCoef<mint> c(1000010);
    return c.com(n+m, n);
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << fixed << setprecision(10);
    lli x, y, ans = 0;
    cin >> x >> y;
    cout << solve(x, y) << endl;
}

Measured memory_bytes: 23680