import java.lang.Math

fun main(args: Array<String>) {
    val mod = 1000000007L

    val (n, a, b) = readInputLine().split(" ").map { it.toInt() }

    val inverse = LongArray(Math.min(n, 200000) + 1)
    val factorialInverse = LongArray(Math.min(n, 200000) + 1)
    inverse[0] = 1L
    inverse[1] = 1L
    factorialInverse[0] = 1L
    factorialInverse[1] = 1L
    for (i in 2 until Math.min(n, 200000) + 1) {
        inverse[i] = (mod - inverse[mod.toInt() % i] * (mod / i.toLong()) % mod)
        factorialInverse[i] = (factorialInverse[i - 1] * inverse[i] % mod)
    }

    // 2^n
    val pow = sortedMapOf(Pair(0, 1L), Pair(1, 2L))
    var powNum = 2
    while (powNum <= n) {
        pow[powNum] = (pow[powNum / 2]!! * pow[powNum / 2]!!) % mod
        powNum *= 2
    }
    pow[powNum] = (pow[powNum / 2]!! * pow[powNum / 2]!!) % mod

    var ans = 1L

    var nTmp = n
    powNum = 1

    while (nTmp != 0) {
        if (nTmp % 2 == 1) {
            ans *= pow[powNum]!!
            ans %= mod
        }
        powNum *= 2
        nTmp /= 2
    }

    ans = (ans + mod - 1L) % mod

    var subTmp = 1L

    for (i in (n - a) + 1..n) {
        subTmp *= i.toLong()
        subTmp %= mod
    }
    subTmp *= factorialInverse[a]
    subTmp %= mod

    ans = (ans + mod - subTmp) % mod

    subTmp = 1L

    for (i in (n - b) + 1..n) {
        subTmp *= i.toLong()
        subTmp %= mod
    }
    subTmp *= factorialInverse[b]
    subTmp %= mod

    ans = (ans + mod - subTmp) % mod

    println(ans)
}

fun readInputLine(): String {
    return readLine()!!
}
