import sys
from functools import reduce
from operator import mul
from typing import Callable, ClassVar, Sequence, Type, TypeVar


T = TypeVar('T', bound='ModIntBase')


class ModIntBase:
    value: int
    mod: ClassVar[int]
    fac: ClassVar[Sequence[int]] = ()
    inv: ClassVar[Sequence[int]] = ()
    finv: ClassVar[Sequence[int]] = ()

    def __init__(self, value: int) -> None:
        self.value = value % self.mod

    def __hash__(self) -> int:
        return hash((self.value, self.mod))

    def __eq__(self, other) -> bool:
        if isinstance(other, self.__class__):
            return self.value == other.value
        else:
            return NotImplemented

    def __ne__(self, other) -> bool:
        if isinstance(other, self.__class__):
            return self.value != other.value
        else:
            return NotImplemented

    # TODO: Add type hints
    def __add__(self, other):
        if isinstance(other, self.__class__):
            return self.__class__((self.value + other.value) % self.mod)
        else:
            return NotImplemented

    def __sub__(self, other):
        if isinstance(other, self.__class__):
            return self.__class__((self.value - other.value) % self.mod)
        else:
            return NotImplemented

    def __mul__(self, other):
        if isinstance(other, self.__class__):
            return self.__class__(self.value * other.value % self.mod)
        else:
            return NotImplemented

    def __truediv__(self, other):
        if isinstance(other, self.__class__):
            a = other.value
            b = self.mod
            u = 1
            v = 0
            while b:
                t = a // b
                a, b = b, a - t * b
                u, v = v, u - t * v
            return self.__class__(self.value * u % self.mod)
        else:
            return NotImplemented

    def __pow__(self, other):
        if isinstance(other, self.__class__):
            v = 1
            a = self.value
            b = other.value
            mod = self.mod
            while b > 0:
                if b & 1:
                    v = v * a % mod
                a = a * a % mod
                b >>= 1
            return self.__class__(v)
        else:
            return NotImplemented

    @classmethod
    def comb(cls, n: int, k: int):
        if n < k:
            return cls(0)
        if n < 0 or k < 0:
            return cls(0)

        if n < len(cls.fac):
            return cls(cls.fac[n] * (cls.finv[k] * cls.finv[n - k] % cls.mod) % cls.mod)
        else:
            k = min(k, n - k)
            a = reduce(mul, map(cls, range(n - k + 1, n + 1)))
            b = reduce(mul, map(cls, range(1, k + 1)))
            return a / b

    def __repr__(self) -> str:
        return f'{self.__class__.__name__}({self.value!r})'

    def __str__(self) -> str:
        return str(self.value)


class ModInt(ModIntBase):
    mod = 1000000007  # 10 ** 9 + 7



def resolve(in_):
    N, A, B = map(int, in_.readline().split())
    
    c = ModInt(2) ** ModInt(N) - ModInt(1)
    a = ModInt.comb(N, A)
    b = ModInt.comb(N, B)
    
    return c - a - b


def main():
    answer = resolve(sys.stdin.buffer)
    print(answer)


if __name__ == '__main__':
    main()


### FIXED CODE ###

import sys
from functools import reduce
from operator import mul


class ModIntMeta(type):
    def __new__(cls, name, bases, classdict):
        ret = super().__new__(cls, name, bases + (_ModIntMixIn,), classdict)
        max_ = ret._max = classdict.get('_max', 510000)
        mod = ret._mod = classdict.get('_mod', 10 ** 9 + 7)

        fac = ret._fac = [0] * max_
        finv = ret._finv = [0] * max_
        inv = ret._inv = [0] * max_

        fac[0] = fac[1] = 1
        finv[0] = finv[1] = 1
        inv[1] = 1
        for i in range(2, max_):
            fac[i] = fac[i - 1] * i % mod
            inv[i] = mod - inv[mod % i] * (mod // i) % mod
            finv[i] = finv[i - 1] * inv[i] % mod
        
        return ret


class _ModIntMixIn:
    _max: int
    _mod: int

    def __init__(self, value):
        self._value = value % self._mod
    
    def __int__(self):
        return self._value

    def __hash__(self):
        return hash((self._value, self._mod))

    def __lt__(self, other):
        if isinstance(other, self.__class__):
            return self._value < other._value
        else:
            return NotImplemented

    def __le__(self, other):
        if isinstance(other, self.__class__):
            return self._value <= other._value
        else:
            return NotImplemented

    def __eq__(self, other):
        if isinstance(other, self.__class__):
            return self._value == other._value
        else:
            return NotImplemented

    def __ne__(self, other):
        if isinstance(other, self.__class__):
            return self._value != other._value
        else:
            return NotImplemented

    def __gt__(self, other):
        if isinstance(other, self.__class__):
            return self._value > other._value
        else:
            return NotImplemented

    def __ge__(self, other):
        if isinstance(other, self.__class__):
            return self._value >= other._value
        else:
            return NotImplemented

    def __add__(self, other):
        if isinstance(other, self.__class__):
            return self.__class__(self._value + other._value % self._mod)
        else:
            return NotImplemented
    
    def __sub__(self, other):
        if isinstance(other, self.__class__):
            return self.__class__(self._value - other._value % self._mod)
        else:
            return NotImplemented
    
    def __mul__(self, other):
        if isinstance(other, self.__class__):
            return self.__class__(self._value * other._value % self._mod)
        else:
            return NotImplemented
    
    def __truediv__(self, other):
        if isinstance(other, self.__class__):
            a = other._value
            b = self._mod
            u = 1
            v = 0
            while b:
                t = a // b
                a, b = b, a - t * b
                u, v = v, u - t * v
            return self.__class__(self._value * u % self._mod)
        else:
            return NotImplemented

    def __pow__(self, other):
        if isinstance(other, self.__class__):
            v = 1
            a = self._value
            b = other._value
            mod = self._mod
            while b > 0:
                if b & 1:
                    v = v * a % mod
                a = a * a % mod
                b >>= 1
            return self.__class__(v)
        else:
            return NotImplemented

    @classmethod
    def comb(cls, n: int, k: int):
        if n < k:
            return 0
        if n < 0 or k < 0:
            return 0

        if n < cls._max:
            return cls(cls._fac[n] * (cls._finv[k] * cls._finv[n - k] % cls._mod) % cls._mod)
        else:
            a = reduce(mul, map(ModInt, range(n - k + 1, n + 1)))
            b = reduce(mul, map(ModInt, range(1, k + 1)))
            return a / b

    def __repr__(self):
        return f'{self.__class__.__name__}({self._value!r})'

    def __str__(self):
        return f'{self._value}'


class ModInt(metaclass=ModIntMeta):
    _max = 2


def resolve(in_):
    N, A, B = map(int, in_.readline().split())
    
    c = ModInt(2) ** ModInt(N) - ModInt(1)
    a = ModInt.comb(N, A)
    b = ModInt.comb(N, B)
    
    return c - a - b


def main():
    answer = resolve(sys.stdin.buffer)
    print(answer)


if __name__ == '__main__':
    main()