/*
このコード、と～おれ!
Be accepted!
∧＿∧　
（｡･ω･｡)つ━☆・*。
⊂　　 ノ 　　　・゜+.
　しーＪ　　　°。+ *´¨)
 　　　　　　　　　.· ´¸.·*´¨) ¸.·*¨)
		  　　　　　　　　　　(¸.·´ (¸.·'* ☆
*/

#include <cstdio>
#include <algorithm>
#include <string>
#include <cmath>
#include <cstring>
#include <vector>
#include <numeric>
#include <iostream>
#include <random>
#include <map>
#include <unordered_map>
#include <queue>
#include <regex>
#include <functional>
#include <complex>
#include <list>
#include <cassert>
#include <iomanip>
#include <set>
#include <stack>
#include <bitset>

////多倍長整数, cpp_intで宣言
//#include <boost/multiprecision/cpp_int.hpp>
//using namespace boost::multiprecision;

//#pragma GCC target ("avx2")
//#pragma GCC optimization ("Ofast")
//#pragma GCC optimization ("unroll-loops")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#define repeat(i, n, m) for(int i = n; i < (m); ++i)
#define rep(i, n) for(int i = 0; i < (n); ++i)
#define printynl(a) printf(a ? "yes\n" : "no\n")
#define printyn(a) printf(a ? "Yes\n" : "No\n")
#define printYN(a) printf(a ? "YES\n" : "NO\n")
#define printim(a) printf(a ? "possible\n" : "imposible\n")
#define printdb(a) printf("%.50lf\n", a) //少数出力
#define printLdb(a) printf("%.50Lf\n", a) //少数出力
#define printdbd(a) printf("%.16lf\n", a) //少数出力(桁少なめ)
#define prints(s) printf("%s\n", s.c_str()) //string出力
#define all(x) (x).begin(), (x).end()
#define deg_to_rad(deg) (((deg)/360.0L)*2.0L*PI)
#define rad_to_deg(rad) (((rad)/2.0L/PI)*360.0L)
#define Please return
#define AC 0
#define manhattan_dist(a, b, c, d) (abs(a - c) + abs(b - d)) /*(a, b) から (c, d) のマンハッタン距離 */
#define inf numeric_limits<double>::infinity();
#define linf numeric_limits<long double>::infinity()

using ll = long long;
using ull = unsigned long long;

constexpr int INF = 1073741823;
constexpr int MINF = -1073741823;
constexpr ll LINF = ll(4661686018427387903);
constexpr ll MOD = 1e9 + 7;
constexpr ll mod = 998244353;
constexpr long double eps = 1e-6;
const long double PI = acosl(-1.0L);

using namespace std;

void scans(string& str) {
	char c;
	str = "";
	scanf("%c", &c);
	if (c == '\n')scanf("%c", &c);
	while (c != '\n' && c != -1 && c != ' ') {
		str += c;
		scanf("%c", &c);
	}
}

void scanc(char& str) {
	char c;
	scanf("%c", &c);
	if (c == -1)return;
	while (c == '\n') {
		scanf("%c", &c);
	}
	str = c;
}


double acot(double x) {
	return PI / 2 - atan(x);
}

ll LSB(ll n) { return (n & (-n)); }

template<typename T>
inline T chmin(T& a, const T& b) {
	if (a > b)a = b;
	return a;
}

template<typename T>
inline T chmax(T& a, const T& b) {
	if (a < b)a = b;
	return a;
}

/*-----------------------------------------ここからコード-----------------------------------------*/

/*
* @title modint
* @docs kyopro/docs/modint.md
*/

template<int mod>
struct modint {
	int val;

	modint() : val(0) {};
	modint(ll x) : val(x >= 0 ? x % mod : (mod + x % mod) % mod) {};

	modint& operator=(const modint& x) {
		val = x.val;
		return *this;
	}

	modint& operator+=(const modint& x) {
		val += x.val;
		if (val >= mod)val -= mod;
		return *this;
	}

	modint& operator-=(const modint& x) {
		val += mod - x.val;
		if (val >= mod)val -= mod;
		return *this;
	}

	modint& operator*=(const modint& x) {
		val = (int)((ll)val * (ll)x.val % mod);
		return *this;
	}

	modint& operator/=(const modint& x) {
		int a = x.val, b = mod, u = 1, v = 0, t;
		while (b > 0) {
			t = a / b;
			swap(a -= t * b, b);
			swap(u -= t * v, v);
		}
		*this *= modint(u);
		return *this;
	}

	modint operator++() {
		val = (val + 1 == mod ? 0 : val + 1);
		return *this;
	}

	modint operator--() {
		val = (val == 0 ? mod - 1 : val - 1);
		return *this;
	}

	modint operator+(const modint& x) const {
		return (modint(*this) += x);
	}

	modint operator-(const modint& x) const {
		return (modint(*this) -= x);
	}

	modint operator*(const modint& x) const {
		return (modint(*this) *= x);
	}

	modint operator/(const modint& x) const {
		return (modint(*this) /= x);
	}

	bool operator==(const modint& x)const {
		return (val == x.val);
	}

	bool operator!=(const modint& x)const {
		return (val != x.val);
	}

	bool operator<(const modint& x)const {
		return (val < x.val);
	}

	bool operator>(const modint& x)const {
		return (val > x.val);
	}

	modint pow(ll n) {
		modint ret(1), a(val);
		while (n > 0) {
			if (n % 2) ret *= a;
			a *= a;
			n /= 2;
		}
		return ret;
	}

	static int getmod() { return mod; };
};

using ModInt = modint<MOD>;
using Modint = modint<mod>;

template<typename T>
struct comb {
	int siz, Mod;

	vector<T> fac, inv, facinv;

	//siz <= 1e7 くらい
	comb(const int &siz, const int &Mod) : siz(siz), Mod(Mod) {
		fac.assign(siz + 1, 0);
		inv.assign(siz + 1, 0);
		facinv.assign(siz + 1, 0);
		fac[0] = fac[1] = facinv[0] = facinv[1] = inv[1] = 1;
		for (int i = 2; i <= siz; ++i) {
			fac[i] = fac[i - 1] * i % Mod;
			inv[i] = Mod - inv[Mod % i] * (Mod / i) % Mod;
			facinv[i] = facinv[i - 1] * inv[i] % Mod;
		}
	}

	T query(const int& n, const int& r) {
		return (n < r or n < 0 or r < 0) ? 0 : ((fac[n] * (facinv[r] * facinv[n - r] % Mod)) % Mod);
	}
};


int main() {

	int x, y;
	scanf("%d%d", &x, &y);
	ModInt ans = 1;
	comb<ll> c(12345678, MOD);
	if ((x + y) % 3)ans = 0;
	else {
		if ((2 * y - x) / 3 < 0 or (2 * x - y) / 3 < 0)ans = 0;
		else ans = c.query((x + y) / 3, (2 * y - x) / 3);
	}
	printf("%d\n", ans.val);
	Please AC;
}


Measured memory_bytes: 292668