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

#define int long long
typedef pair<int, int> P;
#define mod 1000000007
#define INF (1LL<<60)

#define rep(i,n) for(int i=0, i##_len=(n); i<i##_len; ++i)
#define repi(itr, ds) for (auto itr = ds.begin(); itr != ds.end(); itr++)
#define YES puts("YES")
#define Yes puts("Yes")
#define NO  puts("NO")
#define No  puts("No")
int gcd(int a, int b) { return b ? gcd(b, a % b) : a; }

const int dx[4] = { 1, 0, -1, 0 };
const int dy[4] = { 0, 1, 0, -1 };


#if 1
//-------------
// DUMPマクロ
// https://www.creativ.xyz/dump-cpp-652/

// vector
template <typename T>
istream & operator>>(istream & is, vector<T> & vec) {
	for (T& x : vec) is >> x;
	return is;
}
// pair
template <typename T, typename U>
ostream& operator<<(ostream& os, pair<T, U>& pair_var) {
	os << "(" << pair_var.first << ", " << pair_var.second << ")";
	return os;
}
// vector
template <typename T>
ostream& operator<<(ostream& os, const vector<T>& vec) {
	os << "{";
	for (int i = 0; i < vec.size(); i++) {
		os << vec[i] << (i + 1 == vec.size() ? "" : ", ");
	}
	os << "}";
	return os;
}
// map
template <typename T, typename U>
ostream& operator<<(ostream& os, map<T, U>& map_var) {
	os << "{";
	repi(itr, map_var) {
		os << *itr;
		itr++;
		if (itr != map_var.end()) os << ", ";
		itr--;
	}
	os << "}";
	return os;
}
// set
template <typename T>
ostream& operator<<(ostream& os, set<T>& set_var) {
	os << "{";
	repi(itr, set_var) {
		os << *itr;
		itr++;
		if (itr != set_var.end()) os << ", ";
		itr--;
	}
	os << "}";
	return os;
}

#define DUMPOUT cerr

void dump_func() {
	DUMPOUT << endl;
}
template <class Head, class... Tail>
void dump_func(Head&& head, Tail&& ... tail) {
	DUMPOUT << head;
	if (sizeof...(Tail) > 0) {
		DUMPOUT << ", ";
	}
	dump_func(std::move(tail)...);
}
#ifdef _DEBUG
#define DEB
#define dump(...)                                                              \
    DUMPOUT << "  " << string(#__VA_ARGS__) << ": "                            \
            << "[" << to_string(__LINE__) << ":" << __FUNCTION__ << "]"        \
            << endl                                                            \
            << "    ",                                                         \
        dump_func(__VA_ARGS__)
#else
#define DEB if (false)
#define dump(...)
#endif
#endif

// ax+by=1の解
int extgcd(int a, int b, int& x, int& y) {
	int d = a;
	if (b != 0) {
		d = extgcd(b, a % b, y, x);
		y -= (a / b) * x;
	}
	else {
		x = 1; y = 0;
	}
	return d;
}

// mod mでのaの逆数
int mod_inverse(int a, int m) {
	int x, y;
	extgcd(a, m, x, y);
	return (m + x % m) % m;
}
// nの階乗 mod p
int factorial(int n, int p) {
	int r = 1;
	for (int i = 1; i <= n; i++)
		r = (r * i) % p;
	return r;
}

// nPr mod p
int permutation(int n, int r, int p) {
	int a = 1;
	for (int i = n - r + 1; i <= n; i++)
		a = (a * i) % p;
	return a;
}

// nCr mod p
int combination(int n, int r, int p) {
	if (r == 0 || r == n) return 1;
	if (r > n) return 0;
	if (r > n / 2) r = n - r;
	int numerator = permutation(n, r, p);
	int denominator = factorial(r, p) % p;
	int inv = mod_inverse(denominator, p);
	return (numerator * inv) % p;
}

signed main() {

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

	int A_B = (X + Y) / 3;
	int A = X - A_B;
	int B = A_B - A;

	if(A<0 || B<0) { cout << 0 << endl; return 0; }

	cout << combination(A + B, A, mod) << endl;


	return 0;
}


Measured memory_bytes: 256