/*
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*/
#include "bits/stdc++.h"
using namespace std;
#define ok1 printf("ok1\n")
#define ok2 printf("ok2\n")
#define M 1000000000000000000LL
#define rep(i,n) for(int i=0;i<n;++i)
#define REP(i,s,n) for(int i=(s);i<(n);++i)
#define repr(i,n) for(int i=n-1;i>=0;--i)
#define REPR(i,s,n) for(int i=(s);i>=(n);--(i))
#define all(a) (a).begin(),(a).end()
#define reall(a) (a).rbegin(),(a).rend()
#define pb emplace_back //emplace_backの方が速いが使い慣れてないため
#define DOUBLE fixed << setprecision(15)
#define fi first
#define se second
#define mp make_pair
#define mt make_tuple
#define BIT(n,m)(((n)>>(m))&1)
const double pi = acos(-1.0);
typedef vector<int> vi;
typedef vector<string> vs;
typedef long long ll;
typedef vector<ll> vll;
typedef vector<vi> vvi;
typedef vector<vll> vvll;
typedef vector<char> vc;
typedef vector<double> vd;
typedef vector<bool> vb;
typedef deque<ll> dll;
typedef pair<ll, ll> P;
typedef vector<P> vP;
const ll mod = 1e9 + 7;
//const ll mod = 998244353;
ll dy[4] = { 1,0,-1,0 };
ll dx[4] = { 0,1,0,-1 };
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }
/*
template< typename T >
using Edges = vector< edge< T > >;
template< typename T >
using WeightedGraph = vector< Edges< T > >;
using UnWeightedGraph = vector< vector< int > >;
template< typename T >
using Matrix = vector< vector< T > >;
*/
bool out_check(ll a, ll b) { return (0 <= a && a < b); }
void addmod(ll &a, ll &b) { a = (a + b) % mod; }
double pitagoras(ll a,ll b,ll c,ll d) {
	double dx = a - b,dy = c - d;
	return pow(dx * dx + dy * dy, 0.5);
}
void Pvi(vi v) {
	puts("vll------------------------------------------------");
	rep(i, v.size()) cout << v[i] << " "; puts("");
	puts("------------------------------------------------");
}
void Pvll(vll v) {
	puts("vll------------------------------------------------");
	rep(i, v.size()) cout << v[i] << " "; puts("");
	puts("------------------------------------------------");
}
void Pvvll(vvll v) {
	puts("vvll------------------------------------------------");
	rep(i, v.size()) { rep(j, v[i].size()) cout << v[i][j] << " "; cout << endl; }
	puts("------------------------------------------------");
}
void Pvs(vs s) {
	puts("vs------------------------------------------------");
	rep(i, s.size()) { rep(j, s[i].size()) cout << s[i][j] << " "; cout << endl; }
	puts("------------------------------------------------");
}

void Yes(bool x) { cout << ((x) ? "Yes\n" : "No\n"); }
void YES(bool x) { cout << ((x) ? "YES\n" : "NO\n"); }
void yes(bool x) { cout << ((x) ? "yes\n" : "no\n"); }
void Yay(bool x) { cout << ((x) ? "Yay!\n" : ":(\n"); }

ll  n, m, d, e, r, l, k, h, ans, ret = M;
bool flag = false, flag2 = false, flag3 = false;
//string s, t, u;

#define MAX_N 2000010
ll factorial[MAX_N];
void make_factorial_table() {
	factorial[0] = 1;
	for (int i = 1; i < MAX_N; i++) {
		factorial[i] = factorial[i - 1] * i%mod;
	}
}

ll bisection_power(ll x, ll y) {
	if (y == 0) { return 1; }
	ll t = bisection_power(x*x%mod, y / 2);
	if (y % 2 == 1) { t = t * x%mod; }
	return t;
}

ll nCr(int n, int r) {
	if (n<r || n <= 0 || r<0) { return 0; }
	ll a = factorial[n];
	ll b = a * bisection_power(factorial[r], (mod - 2)) % mod;
	ll c = b * bisection_power(factorial[n - r], mod - 2) % mod;
	return c % mod;
}
int main() {
	cin.tie(0); ios::sync_with_stdio(false);//not intractive
	ll t,x,y;
	cin >> x >> y;
	if ((x + y) % 3) {
		puts("0"); return 0;
	}
	t = (x + y) / 3;
	x -= t, y -= y;
	if (x < 0 || y < 0) {
		puts("0"); return 0;
	}
	make_factorial_table();
	cout << nCr(t, x) << endl;
	return 0;
}


Measured memory_bytes: 15872