n, a, b = list(map(int, input().split()))

mod = 10**9+7



def factorial_mod(x, y, mod):

    factorial = 1

    for i in range(x,y+1):

        factorial *= i

        factorial %= mod

    return factorial





#conbinationを何回も求める場合はfactorial_k,nkをあらかじめ計算し, リストに入れておけば良い

def n_C_k(n,k,mod):

    factorial_nk = factorial_mod(n-k+1, n, mod)

    factorial_k = factorial_mod(1,k,mod)

    conbi=factorial_nk*pow(factorial_k, mod-2, mod)

    return conbi%mod



ans = (pow(2, n, mod)-1-n_C_k(n, a, mod)-n_C_k(n, b, mod))%mod

print(ans)

n, a, b = list(map(int, input().split()))

mod = 10**9+7

"""

def factorial_mod(x, y, mod):

    factorial = 1

    for i in range(x,y+1):

        factorial *= i

        factorial %= mod

    return factorial





#conbinationを何回も求める場合はfactorial_k,nkをあらかじめ計算し, リストに入れておけば良い

def n_C_k(n,k,mod):

    factorial_nk = factorial_mod(n-k+1, n, mod)

    factorial_k = factorial_mod(1,k,mod)

    conbi=factorial_nk*pow(factorial_k, mod-2, mod)

    return conbi%mod



ans = (pow(2, n, mod)-1-n_C_k(n, a, mod)-n_C_k(n, b, mod))%mod

print(ans)

"""



#n!を求める

def factorial_mod(n, mod):

    x = 1

    for i in range(1, n+1):

        x *= i

        x %= mod

    return x



#n_P_kを求める

def permutation_mod(n, k, mod):

    x = 1

    for i in range(n-k+1, n+1): #k回for文を回す

        x *= i

        x %= mod

    return x



#conbinationを何回も求める場合はfactorial_k,nkをあらかじめ計算し, リストに入れておけば良い

def n_C_k(n, k, mod): #O(min(k, n-k))

    k = min(k, n-k)

    n_P_k = permutation_mod(n, k, mod)

    factorial_k = factorial_mod(k, mod)

    conbi=n_P_k * pow(factorial_k, mod-2, mod)

    return conbi % mod



ans = (pow(2, n, mod)-1-n_C_k(n, a, mod)-n_C_k(n, b, mod))%mod

print(ans)
n, a, b = list(map(int, input().split()))
mod = 10**9 + 7


def factorial_mod(x, y, mod):
    factorial = 1
    for i in range(x, y + 1):
        factorial *= i
        factorial %= mod
    return factorial


# conbinationを何回も求める場合はfactorial_k,nkをあらかじめ計算し, リストに入れておけば良い
def n_C_k(n, k, mod):
    factorial_nk = factorial_mod(n - k + 1, n, mod)
    factorial_k = factorial_mod(1, k, mod)
    conbi = factorial_nk * pow(factorial_k, mod - 2, mod)
    return conbi % mod


ans = (pow(2, n, mod) - 1 - n_C_k(n, a, mod) - n_C_k(n, b, mod)) % mod
print(ans)

n, a, b = list(map(int, input().split()))
mod = 10**9 + 7
"""
def factorial_mod(x, y, mod):
    factorial = 1
    for i in range(x,y+1):
        factorial *= i
        factorial %= mod
    return factorial
#conbinationを何回も求める場合はfactorial_k,nkをあらかじめ計算し, リストに入れておけば良い
def n_C_k(n,k,mod):
    factorial_nk = factorial_mod(n-k+1, n, mod)
    factorial_k = factorial_mod(1,k,mod)
    conbi=factorial_nk*pow(factorial_k, mod-2, mod)
    return conbi%mod
ans = (pow(2, n, mod)-1-n_C_k(n, a, mod)-n_C_k(n, b, mod))%mod
print(ans)
"""
# n!を求める
def factorial_mod(n, mod):
    x = 1
    for i in range(1, n + 1):
        x *= i
        x %= mod
    return x


# n_P_kを求める
def permutation_mod(n, k, mod):
    x = 1
    for i in range(n - k + 1, n + 1):  # k回for文を回す
        x *= i
        x %= mod
    return x


# conbinationを何回も求める場合はfactorial_k,nkをあらかじめ計算し, リストに入れておけば良い
def n_C_k(n, k, mod):  # O(min(k, n-k))
    k = min(k, n - k)
    n_P_k = permutation_mod(n, k, mod)
    factorial_k = factorial_mod(k, mod)
    conbi = n_P_k * pow(factorial_k, mod - 2, mod)
    return conbi % mod


ans = (pow(2, n, mod) - 1 - n_C_k(n, a, mod) - n_C_k(n, b, mod)) % mod
print(ans)

- - +""" -    for i in range(x, y + 1): +    for i in range(x,y+1): +#conbinationを何回も求める場合はfactorial_k,nkをあらかじめ計算し, リストに入れておけば良い +def n_C_k(n,k,mod): +    factorial_nk = factorial_mod(n-k+1, n, mod) +    factorial_k = factorial_mod(1,k,mod) +    conbi=factorial_nk*pow(factorial_k, mod-2, mod) +    return conbi%mod +ans = (pow(2, n, mod)-1-n_C_k(n, a, mod)-n_C_k(n, b, mod))%mod +print(ans) +""" +# n!を求める +def factorial_mod(n, mod): +    x = 1 +    for i in range(1, n + 1): +        x *= i +        x %= mod +    return x + + +# n_P_kを求める +def permutation_mod(n, k, mod): +    x = 1 +    for i in range(n - k + 1, n + 1):  # k回for文を回す +        x *= i +        x %= mod +    return x -def n_C_k(n, k, mod): -    factorial_nk = factorial_mod(n - k + 1, n, mod) -    factorial_k = factorial_mod(1, k, mod) -    conbi = factorial_nk * pow(factorial_k, mod - 2, mod) +def n_C_k(n, k, mod):  # O(min(k, n-k)) +    k = min(k, n - k) +    n_P_k = permutation_mod(n, k, mod) +    factorial_k = factorial_mod(k, mod) +    conbi = n_P_k * pow(factorial_k, mod - 2, mod)