def main():

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

    MOD = 10**9 +7

    s = pow(2,n,MOD)-1

    P_ni = 1

    F_i = 1



    s = s - comb_mod(n,a,MOD)

    s = s - comb_mod(n,b,MOD)



    print((s%MOD))



def comb_mod(n, k, mod):

    numerator = 1

    denominator = 1

    for i in range(k):

        numerator = (numerator * (n - i)) % mod

        denominator = (denominator * (i + 1)) % mod



    return (numerator * pow(denominator, mod - 2, mod)) % mod





if __name__=='__main__':

    main()

def main():

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

    MOD = 10**9 +7

    s = pow(2,n,MOD)-1

    

    print((comb_mod(n,MOD,a,b,s)))



def comb_mod(n, mod,a,b,s):

    numerator = 1

    denominator = 1

    for i in range(b):

        numerator = (numerator * (n - i)) % mod

        denominator = (denominator * (i + 1)) % mod

        if i == a-1 or i == b-1:

            s = s - (numerator * pow(denominator, mod - 2, mod)) % mod

    return s%mod





if __name__=='__main__':

    main()

def main():
    n, a, b = list(map(int, input().split()))
    MOD = 10**9 + 7
    s = pow(2, n, MOD) - 1
    P_ni = 1
    F_i = 1
    s = s - comb_mod(n, a, MOD)
    s = s - comb_mod(n, b, MOD)
    print((s % MOD))


def comb_mod(n, k, mod):
    numerator = 1
    denominator = 1
    for i in range(k):
        numerator = (numerator * (n - i)) % mod
        denominator = (denominator * (i + 1)) % mod
    return (numerator * pow(denominator, mod - 2, mod)) % mod


if __name__ == "__main__":
    main()

def main():
    n, a, b = list(map(int, input().split()))
    MOD = 10**9 + 7
    s = pow(2, n, MOD) - 1
    print((comb_mod(n, MOD, a, b, s)))


def comb_mod(n, mod, a, b, s):
    numerator = 1
    denominator = 1
    for i in range(b):
        numerator = (numerator * (n - i)) % mod
        denominator = (denominator * (i + 1)) % mod
        if i == a - 1 or i == b - 1:
            s = s - (numerator * pow(denominator, mod - 2, mod)) % mod
    return s % mod


if __name__ == "__main__":
    main()

-    P_ni = 1 -    F_i = 1 -    s = s - comb_mod(n, a, MOD) -    s = s - comb_mod(n, b, MOD) -    print((s % MOD)) +    print((comb_mod(n, MOD, a, b, s))) -def comb_mod(n, k, mod): +def comb_mod(n, mod, a, b, s): -    for i in range(k): +    for i in range(b): -    return (numerator * pow(denominator, mod - 2, mod)) % mod +        if i == a - 1 or i == b - 1: +            s = s - (numerator * pow(denominator, mod - 2, mod)) % mod +    return s % mod