#define MOD 1000000007

#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;

long pow(long a, long b) {
	if (!b) return 1;
	long c = pow(a, b / 2);
	if (b % 2) c = a * c % MOD * c % MOD;
	else c = c * c % MOD;
	return c;
}

int main() {
	int X, Y;
	cin >> X >> Y;
	if ((X * 2 - Y) % 3 || (Y * 2 - X) % 3) cout << 0;
	else {
		int a = (X * 2 - Y) / 3, b = (Y * 2 - X) / 3;
		if (a < 0 || b < 0) cout << 0;
		else {
			vector<long> c(max(a + b, a) + 1, 1), d(max(a + b, a) + 1, 1);
			for (int i = 1; i <= max(a + b, a); i++) {
				c[i] = c[i - 1] * i % MOD;
				d[i] = pow(c[i], MOD - 2);
			}
			cout << c[a + b] * d[a] % MOD * d[b] % MOD;
		}
	}
}