#include <bits/stdc++.h>
using namespace std;
#define INF 1<<30
#define endl '\n'
#define maxn 100005
#define tc printf("Case %d: ", cs)
#define tcn printf("Case %d:\n", cs);
#define FASTIO ios_base::sync_with_stdio(false), cin.tie(0), cout.tie(0);
typedef long long ll;
const double PI = acos(-1.0);

#define dbg1(x) cerr << #x << " = " << x << endl;
#define dbg2(x, y) cerr << #x << " = " << x << ", " << #y << " = " << y << endl;
#define dbg3(x, y, z) cerr << #x << " = " << x << ", " << #y << " = " << y << ", " << #z << " = " << z << endl;
#define dbg4(w,x, y, z) cerr << #w << " = " << w << ", " <<#x << " = " << x << ", " << #y << " = " << y << ", " << #z << " = " << z << endl;

template < typename F, typename S >
ostream& operator << ( ostream& os, const pair< F, S > & p ) {
    return os << "(" << p.first << ", " << p.second << ")";
}

template < typename T >
ostream &operator << ( ostream & os, const vector< T > &v ) {
    os << "{";
    for (auto it = v.begin(); it != v.end(); ++it) {
        if ( it != v.begin() ) os << ", ";
        os << *it;
    }
    return os << "}";
}

template < typename T >
ostream &operator << ( ostream & os, const set< T > &v ) {
    os << "[";
    for (auto it = v.begin(); it != v.end(); ++it) {
        if ( it != v.begin()) os << ", ";
        os << *it;
    }
    return os << "]";
}

template < typename F, typename S >
ostream &operator << ( ostream & os, const map< F, S > &v ) {
    os << "[";
    for (auto it = v.begin(); it != v.end(); ++it) {
        if ( it != v.begin() ) os << ", ";
        os << it -> first << " = " << it -> second ;
    }
    return os << "]";
}

#define dbg(args...) do {cerr << #args << " : "; faltu(args); } while(0)

clock_t tStart = clock();
#define timeStamp dbg("Execution Time: ", (double)(clock() - tStart)/CLOCKS_PER_SEC)

void faltu () { cerr << endl; }

template <typename T>
void faltu( T a[], int n ) {
    for (int i = 0; i < n; ++i) cerr << a[i] << ' ';
    cerr << endl;
}

template <typename T, typename ... hello>
void faltu( T arg, const hello &... rest) { cerr << arg << ' '; faltu(rest...); }
// Program showing a policy-based data structure.
#include <ext/pb_ds/assoc_container.hpp> // Common file 
#include <ext/pb_ds/tree_policy.hpp>
#include <functional> // for less 
#include <iostream>
using namespace __gnu_pbds;
using namespace std;
// GNU link : https://goo.gl/WVDL6g
typedef tree<int, null_type, less_equal<int>, rb_tree_tag,
        tree_order_statistics_node_update>
        new_data_set;

/**___________________________________________________**/

const int N = 1e6 + 5;
const ll mod = 1e9 + 7;
ll fact[N];
ll factInv[N];

ll mul(ll a, ll b)
{
    return (a * b) % mod;
}

ll power(ll a, ll b)    //a is base, b is exponent
{
    if (b == 0)
        return 1;
    if (b == 1)
        return a;
    if (b % 2 == 1)
        return (power(a, b - 1) * a) % mod;
    ll q = power(a, b / 2);
    return (q * q) % mod;
}

ll inv(ll base)
{
    return power(base, mod - 2);
}

void initFact()
{
    fact[0] = 1;
    factInv[0] = 1;
    for (int i = 1; i < N; i++) {
        fact[i] = (fact[i - 1] * i) % mod;
        //dbg(fact[i]);
        factInv[i] = inv(fact[i]);
    }
}

ll solve(ll a, ll b)
{
    if (b > a) return 0;
    if (a < 0 || b < 0) return 0;
    ll ret = fact[a];
    ret = mul(ret, factInv[b]);
    ret = mul(ret, factInv[a - b]);
    return ret;
}
/*

*/
int main()
{
    FASTIO
    /*
    #ifndef ONLINE_JUDGE
    freopen("in.txt", "r", stdin);
    freopen("out.txt", "w", stdout);
    freopen("error.txt", "w", stderr);
    #endif
    //*/
    initFact();
    ll x, y;
    cin >> x >> y;
    if ((x + y) % 3) {
        cout << 0 << endl;
        return 0;
    }
    if (max(x, y) > 2 * min(x, y)) {
        cout << 0 << endl;
        return 0;
    }
    ll k = (x + y) / 3;
    x -= k;
    y -= k;
    cout << solve(x + y, x) << endl;
}

Measured memory_bytes: 16000