fun main(args: Array<String>) {
    var (x, y) = readIntList()

    if ((x + y) % 3 != 0) {
        println(0)
        return
    }
    val n = (x + y) / 3
    x -= n
    y -= n
    if (x < 0 || y < 0) {
        println(0)
        return
    }
    val mod = 1_000_000_007L
    val comb = CombinationModPrime(x + y, mod)
    println(comb.operate(x + y, x))
}

// Tools
fun readString() = readLine()!!
fun readInt() = readLine()!!.toInt()
fun readLong() = readLine()!!.toLong()
fun readStringList() = readLine()!!.split(" ")
fun readIntList() = readLine()!!.split(" ").map(String::toInt)
fun readLongList() = readLine()!!.split(" ").map(String::toLong)

fun Long.modPow(t: Long, mod: Long): Long {
    if (t == 0L) return 1L
    var a = this.modPow(t shr 1, mod)
    a *= a
    a %= mod
    if (t and 1 == 1L) {
        a *= this
        a %= mod
    }
    return a
}

// mod pの逆元 (pは素数)
fun Long.modInverse(mod: Long) = this.modPow(mod - 2L, mod)

class CombinationModPrime(private val n: Int, private val mod: Long) {
    private val fact = Array(n + 1) { 0L }
    private val ifact = Array(n + 1) { 0L }

    init {
        fact[0] = 1
        for (i in 1..n) {
            val tmp = fact[i - 1] * i.toLong()
            fact[i] = tmp % mod
        }
        ifact[n] = fact[n].modInverse(mod)
        for (i in n downTo 1) {
            val tmp = ifact[i].toLong() * i.toLong()
            ifact[i - 1] = tmp % mod
        }
    }

    fun operate(n: Int, k: Int): Int {
        if (k < 0 || k > n) return 0
        var tmp = fact[n] * ifact[k]
        tmp %= mod
        tmp *= ifact[n - k]
        tmp %= mod
        return tmp.toInt()
    }
}