import std.stdio, std.conv, std.functional, std.string;
import std.algorithm, std.array, std.container, std.range, std.typecons;
import std.numeric, std.math, std.random;
import core.bitop;

string FMT_F = "%.10f";

static File _f;
void file_io(string fn) { _f = File(fn, "r"); }
static string[] s_rd;
T _RD(T = long)() { while(!s_rd.length) s_rd = readln.chomp.split; string res = s_rd[0]; s_rd.popFront; return res.to!T; }
T _RD(T = long)(File f) { while(!s_rd.length) s_rd = f.readln.chomp.split; string res = s_rd[0]; s_rd.popFront; return res.to!T; }
T[] _RDA(T = long)(T fix = 0) { auto r = readln.chomp.split.to!(T[]); r[] += fix; return r; }
T[] _RDA(T = long)(File f, T fix = 0) { auto r = f.readln.chomp.split.to!(T[]); r[] += fix; return r; }
T RD(T = long)() { if (_f.isOpen) return _RD!T(_f); else return _RD!T; }
T[] RDA(T = long)(T fix = 0) { if (_f.isOpen)  return _RDA!T(_f, fix); else return _RDA!T(fix); }

size_t[] MAKE_IDX(alias less = "a < b", Range)(Range range) { auto idx = new size_t[](range.length); makeIndex!(less)(range, idx); return idx;}
size_t MIN_POS(alias less = "a < b", Range)(Range range) { auto r = minPos!(less)(range); return range.length - r.length; }

bool inside(T)(T x, T b, T e) { return x >= b && x < e; }
long lcm(long x, long y) { return x * (y / gcd(x, y)); }

long mod = 10^^9 + 7;
//long mod = 998244353;
//long mod = 1_000_003;
void moda(ref long x, long y) { x = (x + y) % mod; }
void mods(ref long x, long y) { x = ((x + mod) - (y % mod)) % mod; }
void modm(ref long x, long y) { x = (x * y) % mod; }

struct Cmb
{
	void init(long n)
	{
		long powmod(long a, long p)
		{
			long ans = 1;
			long mul = a;
			while (p > 0)
			{
				if ((p & 1) == 1)
					ans.modm(mul);
				p >>= 1;
				mul.modm(mul);
			}
			return ans;
		}

		++n;
		fact = new long[2][](n);
		fact[0][0] = 1;
		foreach (i; 1..n)
		{
			fact[i][0] = fact[i-1][0];
			fact[i][0].modm(i);
		}
		fact[n-1][1] = powmod(fact[n-1][0], mod - 2);
		foreach_reverse (i; 0..n-1)
		{
			fact[i][1] = fact[i+1][1];
			fact[i][1].modm(i+1);
		}
	}

	long get(long n, long r)
	{
		long res = fact[n][0];
		res.modm(fact[r][1]);
		res.modm(fact[n-r][1]);
		return res;
	}

	long[2][] fact;
}

void main()
{
	auto X = RD;
	auto Y = RD;

	if ((X+Y) % 3 == 0 && min(X, Y)*2 >= max(X, Y))
	{
		Cmb cmb;
		cmb.init(max(X, Y));
		auto num = (X+Y) / 3;
		auto a = min(X, Y);
		auto b = max(X, Y);
		auto d = (b - a) / 2;
		auto ans = cmb.get(num, num/2 - d);
		writeln(ans);
	}
	else
		writeln(0);
	stdout.flush();
	debug readln();
}