#include<iostream>
using namespace std;
typedef long long ll;
#define MOD 1000000007

ll mul(ll n){
    ll p;
    p = 1;
    for(int i = 1;i < n+1;i++){
        p = p*i%MOD;
    }
    return p;
}

ll modinv(long long a) {
    long long b = MOD, u = 1, v = 0;
    while (b) {
        long long t = a / b;
        a -= t * b; swap(a, b);
        u -= t * v; swap(u, v);
    }
    u %= MOD; 
    if (u < 0) u += MOD;
    return u;
}

int main(){
    ll x,y;
    cin >> x >> y;
    if((2*x-y)%3 == 0 && (2*y-x)%3 == 0 && 2*x-y >=0 && 2*y-x>=0){
        ll n = (2*x-y)/3;
        ll m = (2*y-x)/3;
        cout << mul(n+m)%MOD*modinv(mul(n))%MOD*modinv(mul(m))%MOD << endl;
    }else{
        cout << 0 << endl;
    }
}