#include <algorithm>
#include <climits>
#include <cmath>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <string>
#include <vector>

using namespace std;

map<long long, int> factorization(long long N) {
	map<long long, int> re;
	while (true) {
		if (N % 2 == 0) {
			N /= 2;
			re[2]++;
			if (N == 1) break;
		}
	}
	if (N > 1) re[N]++;
	for (int loop = 3; (long long)loop * (long long)loop <= N; loop += 2) {
		if (N % loop == 0) {
			N /= loop;
			re[loop]++;
			loop -= 2;
			if (N == 1) break;
		}
	}
	if (N > 1) re[N]++;
	return re;
}

struct Memo {
	long long fact = 0;
	long long fact_inv = 0;
	long long inv = 0;
};
class Combination1 {
private:
	int m_module = 1000000007;
	vector<struct Memo> memo;
public:
	int calculate(int, int);
	Combination1(int, int);
};
int Combination1::calculate(int n, int k) {
	return ((memo[n].fact * memo[k].fact_inv) % m_module * memo[n - k].fact_inv) % m_module;
}
Combination1::Combination1(int memo_max, int module = 1000000007) {
	m_module = module;
	memo.push_back({ 1,1,0 });
	memo.push_back({ 1,1,1 });
	for (int loop = 2; loop <= memo_max; loop++) {
		struct Memo temp;
		temp.fact = (memo[loop - 1].fact * loop) % m_module;
		temp.inv = m_module - (memo[m_module % loop].inv * int(m_module / loop)) % m_module;
		temp.fact_inv = (memo[loop - 1].fact_inv * temp.inv) % m_module;
		memo.push_back(temp);
	}
}

class Combination2 {
private:
	int size = 0;
	bool add(int);
public:
	vector<int> sequence;
	bool next_combination(void);
	Combination2(int, int);
};
bool Combination2::add(int index) {
	if (index == (int)sequence.size() - 1 && sequence[index] == size - 1
		|| index < (int)sequence.size() - 1 && sequence[index] == sequence[index + 1] - 1) {
		if (index == 0) {
			return false;
		}
		else {
			bool re = add(index - 1);
			sequence[index] = sequence[index - 1] + 1;
			return re;
		}
	}
	else {
		sequence[index]++;
		return true;
	}
}
bool Combination2::next_combination(void) {
	return (sequence.size() == 0) ? false : add(sequence.size() - 1);
}
Combination2::Combination2(int n, int r) {
	size = n;
	for (int loop = 0; loop < r; loop++) sequence.push_back(loop);
	return;
}

void A_Circle(void) {

	int r; cin >> r;
	cout << r * r << flush;
	return;
}

void B_Echo(void) {

	int N; string S; cin >> N >> S;

	cout << ((N % 2 == 0 && S.substr(0, N / 2) == S.substr(N / 2, N / 2)) ? "Yes" : "No") << flush;
	return;
}

void C_Average_Length(void) {

	int N; cin >> N;
	struct Town { int x, y; };
	vector<struct Town> town(N);
	for (struct Town& here :town) cin >> here.x >> here.y;

	vector<int> perm(N);
	double length = 0;
	int counter = 0;
	for (int loop = 0; loop < N; loop++) perm[loop] = loop;
	do {
		for (int loop = 1; loop < N; loop++) {
			length += pow(pow(town[perm[loop]].x - town[perm[loop - 1]].x, 2) + pow(town[perm[loop]].y - town[perm[loop - 1]].y, 2), 0.50);
		}
		counter++;
	} while (next_permutation(perm.begin(), perm.end()));
	cout << setprecision(20) << length / counter << flush;
	return;
}

void D_Knight(void) {

	int X, Y; cin >> X >> Y;
	if ((X + Y) % 3 == 0 && X <= Y * 2 && X * 2 >= Y) {
		class Combination1 com((X + Y) / 3);
		cout << com.calculate((X + Y) / 3, X - (X + Y) / 3) << flush;
	}
	else {
		cout << 0 << flush;
	}
	return;
}

int main(void) {
	
	//A_Circle();
	//B_Echo();
	//C_Average_Length();
	D_Knight();
	return 0;
}


Measured memory_bytes: 26984