;('use strict')

const main = arg => {
  const n = BigInt(parseInt(arg.split(' ')[0], 10))
  const a = BigInt(parseInt(arg.split(' ')[1], 10))
  const b = BigInt(parseInt(arg.split(' ')[2], 10))
  const p = BigInt(Math.pow(10, 9) + 7)

  const modpow = (a, exp, mod) => {
    if (exp == 0n) return BigInt(1)
    if (exp == 1n) return BigInt(a % mod)
    if (exp % 2n == 0) {
      const d = BigInt(modpow(a, exp / 2n, mod) % mod)
      return BigInt(d * d) % mod
    }
    return BigInt(a * modpow(a, exp - 1n, mod)) % mod
  }

  let ret = modpow(2n, BigInt(n), p) - 1n

  let _a1 = 1n
  let _a2 = 1n
  let _b1 = 1n
  let _b2 = 1n

  for (let i = 0n; i < a; i++) {
    _a1 = BigInt(_a1 * (n - i)) % p
    _a2 = BigInt(_a2 * (i + 1n)) % p
  }
  let _a = BigInt(_a1 * modpow(_a2, p - 2n, p)) % p

  for (let i = 0n; i < b; i++) {
    _b1 = BigInt(_b1 * (n - i)) % p
    _b2 = BigInt(_b2 * (i + 1n)) % p
  }
  let _b = BigInt(_b1 * modpow(_b2, p - 2n, p)) % p

  ret -= _a
  ret -= _b
  console.log(ret.toString())
}
main(require('fs').readFileSync('/dev/stdin', 'utf-8'))
